Irrigation Glossary

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A

Adapter

A fitting that connects fittings and pipe of different sizes or thread types.

Air Gap

A backflow prevention system. An Air Gap prevents water from being sucked, or siphoned, back into the water supply. There is a physical space (vertically) between a discharge pipe and the flood-level rim of receiving vessel. The receiving vessel is open and not under pressure.

The air gap must be at least double the diameter of the supply pipe measured vertically above the overflow rim of the receiving vessel. The Air Gap must be 1 inch or greater.

While not always practical, an Air Gap provides the maximum protection available against backflow (and potential contamination of water supply).

Anti-Siphon Valve

An economical irrigation control valve containing an atmospheric vacuum breaker (backflow preventer). This prevents a backflow (siphon) of irrigation water into the main household or commercial water supply. Usually made of brass or plastic, anti-siphon valves are primarily used in residential irrigation systems. They are installed at the beginning of the irrigation zone.

Arc

Portion of a full circle (360) covered by a sprinkler nozzle. Adjustable (variable) arc nozzles can be set from 0 - 360. Spray nozzles are most often designated as Quarter, Half, and Full circle.

Atmospheric Vacuum Breaker

An Atmospheric Vacuum Breaker is a backflow preventer that is installed above the highest point in an irrigation system. It contains a float (air inlet valve) which closes when water is moving in the normal direction, keeping air out of the system. If a siphon begins to form, the float drops to allow air into the system, breaking any potential backflow into the main water supply. Atmospheric Vacuum Breakers should be installed at a minimum of 6" above the highest pipe or outlet in the system.

Automatic Valve

A valve which can be remotely operated either electrically (the most common) or hydraulically. Automatic valves are commonly used as "control valves" for irrigation systems. See also Valve, Bleed Valve.

AVB

Backflow prevention device. See Atmospheric Vacuum Breaker.

 

AWG-UF

Designations for  direct-bury wire used in irrigation installations. The multi-strand wire is run from the irrigation controller to the automatic (electric) solenoid irrigation vales.

AWG stands for American Wire Gauge, and it is a standard used for denoting wire conductor diameter. The lower the AWG, the thicker the conductor.

Uf cable is manufactured with unsulated copper conductors in sizes ranging from AWG 14 through 4/0 AWG and with aluminum or copper-clad aluminum conductors in sizes 12 AWG through 4/0 AWG.

 

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Back Flow

An unintended reverse flow of water from an irrigation system into the main water supply. It is caused by backpressure or a back siphon. Irrigation systems come in contact with many potentially harmful materials including fertilizers, pesticides, bacteria, insects, and animal waste. These contaminates will pollute household water supplies if sucked back in via backflow. 

 

Backpressure can be created by a pump in the system or when pipe/sprinklers in the zone are at a higher elevation than the point of connection to the water source. 

 

Back siphoning can occur if there is a break in the supply pipe and/or a drop in pressure of the supply line. Backflow most commonly occurs when there is a temporary sudden loss of pressure from the main water supply. 

 

A properly installed backflow preventer will prevent backpressure or back siphonage from impacting the main water supply. 

Backflow Preventer

A device installed on an irrigation system to prevent water in the irrigation pipes from flowing back into the main (household) water supply. Irrigation systems come in contact with many potentially harmful materials including fertilizers, pesticides, bacteria, insects, and animal waste. These contaminates will pollute household water supplies if sucked back in via backflow.

Types of Backflow Preventers

Air Gap

An Air Gap is a backflow prevention system that prevents water from being sucked, or siphoned, back into the water supply. There is a physical space (vertically) between a discharge pipe and the flood-level rim of receiving vessel. The receiving vessel is open and not under pressure.

The air gap must be at least double the diameter of the supply pipe measured vertically above the overflow rim of the receiving vessel. The Air Gap must be 1 inch or greater.

While not always practical, an Air Gap provides the maximum protection available against backflow (and potential contamination of water supply).

Atomospheric Vacuum Breaker (AVB)

An Atmospheric Vacuum Breaker is a backflow preventer that is installed above the highest point in an irrigation system. It contains a float (air inlet valve) which closes when water is moving in the normal direction, keeping air out of the system. If a siphon begins to form, the float drops to allow air into the system, breaking any potential backflow into the main water supply. Atmospheric Vacuum Breakers should be installed at a minimum of 6" above the highest pipe or outlet in the system.

Double Check Valve Assembly (DC)

A Double Check Valve (or double check assembly) is a backflow preventer containing two positive-seating check valves assembled in series.  A ball valve or gate valve is installed at each end for isolation and testing of each check valve. Small ball valves, called testcocks, provide locations for attatchment of testing equipment.

The benefit of the double check valve is that it does not need to be installed abouvr the highets head or pipe in the irrigation system. It can be installed underground in a valve box.

Pressure Vacuum Breaker (PVB)

A Pressure Vacuum Breaker (PVB) is a backflow device containing a spring loaded check valve and an independently operating air inlet valve. Since the PVB is not designed to protect aginast backpressure, it must be installed at least 12" above the highest head or pipe in the irrigation system. It provides a better solution against backsiphonage than an atmospheric vacuum breaker as the spring-loaded valve dows not rely on gravity as does the AVB. 

Reduced Pressure Principle Assembly (RP, RPA, RPZ)

A Reduced Pressure Principle Assembly is a backflow device consisting of of two two independently acting check valves and a mechanically independent, hydraulically dependent automatic pressure differential relief valve located between the two check valves. The relief valve maintains a reduced pressure zone between the two check valves that is lower than the supply pressure. A ball valve or gate valve is installed at each end for isolation and testing of each check valve. Four small ball valves, called testcocks, provide locations for attatchment of testing equipment. The RP must be installed 12" above the highest head or pipe in the irrigation system.

Ball Valve

A simple control or shut-off valve containing a rotating ball, with a hole in the middle of it, that controls the flow of water . When the valve is open, the hole is aligned with the flow of water. When the valve is closed (or rotated toward the closed position), the hole is rotated out of open alignment and the water flow is restricted or completely shut off.

Barbed Fitting

A drip irrigation coupler, elbow, tee, or emitter with a barbed end. Barbs fit into holes punched in drip tubing. Barbs have ridges designed to hold the fitting in place.

Black Water

Raw sewage water. It contains human or animal urine and fecal material.

Bleed Valve

Used to manually turn on an automatic valve. a bleed valve is located on or near the top of the valve. It can be a small screw, a lever, or built into the solenoid. When turned, the bleed valve allows water to flow out of the cavity over the internal diaphragm of the valve. This causes a pressure differential and opens the valve. 

If the bleed valve is an external type, a small stream of water will flow from the bleed valve and outside of the valve while it is on. An internal bleed will keep the water inside the valve and empty it into the downstream side of the valve. See also Valve.

Booster Pump

A pump used to increase the water pressure for a household and/or irrigation system. Where water pressure is low or fluctuating, a booster pump is used to maintain strong, even water pressure.

 

Brackish Water

Water with a level of salinity between fresh water and sea water.

Branch Line

In a drip irrigation system, a branch (or lateral) line attaches to the mainline tubing and carries water from the main line to the plant zone. It is usually 1/2" or 1/4" tubing.

Bubbler

Used for deep watering of trees and shrubs. Bubblers are generally installed on 1/2" risers, on a per-plant basis, and bubble water only a short distance from the device. A "flood bubbler" is designed to flood irrigate. A "spider bubbler" or "stream bubbler" sprays "fingers" of water that can reach up to 2 feet and is good for watering trees and shrubs.

Bug Plug

Also called an "Insect Plug", a bug plug is installed in 1/4" drip tubing to keep insects from entering and clogging the tubing. Bug plugs do not restrict the flow of water to plants.

Bushing

Usually a PVC fitting,  a bushing connects pipes and fittings of different sizes. Also called a reducer bushing, it often has male and female ends. They can be found as slip, threaded, or slip x thread fittings.

 

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Cavitation

Cavitation occurs when cavities or bubbles form in the liquid being pumped. Cavities are formed at the low pressure side of the pump (suction side). The bubbles or cavities move into areas of high pressure and implode or collapse on themselves. Water then moves at a high velocity as it contacts pump components. Noise increases and vibrations occur, damaging pump components.

 

Cavitation effects include:

* Increased noise and vibration
* Reduction of pump capacity
* Reduction of pump output pressure
* Drop in pump efficiency

 

Check Valve

An in-line, one-way valve that allows water to flow in one direction only. The valve contains a spring that closes the valve until the water pressure increases to a level greater than the force of the spring. A check valve prevents water from flowing back toward the water source. They are used in sprinklers, irrigation systems and sump pump outflow pipes. 

Class 200

A PVC pipe classification (often written as CL 200), commonly used for lateral water lines. The number represents the water pressure rating (psi) for that pipe. Class 200 pipe is rated for a maximum water pressure of 200 psi. For additional classifications of irrigation pipe  see Shedule 40 and Schedule 80.

 

 

Clock

See Controller

Compression Fitting

Fittings used to connect lengths of 1/2" and 3/4" drip tubing. The tubing is simply inserted into the compression fitting. Glue is not required. See also Poly Pipe.

 

Controller

Also referred to as a clock, or timer, an irrigation controller is an electronic, programmable device that controls the timing of automatic electronic valves in an irrigation sytem. The valves control the flow of water to sprinklers and drip systems. The contoller sends electricty (low voltage) to the valve on the day and time set in the controller schedule and for the duration programmed by the user.

High end controllers employ weather-based controls ( ex. rain sensors, soil moisture monitors, real-time weather data), internet connections, cell phones, and remote controls for use with sophisticated irrigation systems. See also Irrigation Schedule.

Coupler

Also called a coupling, it joins fitings and pipe of like size together. Couplers may be slip, threaded, barbed or compression or combination thereof.

Connecting unlike items is called “adapting”. See Adapter.

Cross

A fitting that connects four sections of pipe at one point forming a cross. Crosses may be slip, threaded, barbed or compression or combination thereof.

Cubic Feet

A measurement of volume, depicted by a cube 1 foot high, 1 foot wide, and 1 foot deep. This measurement is commonly used to determine required materials for landscaping, gardening, and construction. (1 cubic foot is 1728 cubic inches).

To determine cubic feet:

• Measure the length and width of the space.
• Measure the height or depth of the space.
• Multiply length x width x height. 

All of your measurements must be in the same units before multiplying.

To convert cubic inches to cubic feet, divide cubic inches by 1728 (12 in x 12 in x 12 in). You can also convert inches to feet before you multiply by dividing each measurement by 12. (12 inches/foot).

Cubic Meters

A measurement of volume, depicted by a cube 1 meter high, 1 meter wide and 1 meter deep.

To determine cubic meters:

• Measure the length and width of the space.
• Measure the height or depth of the space.
• Multiply length x width x height. 

All of your measurements must be in the same units before multiplying.

1 meter is 3.28 feet.

To convert cubic meters to cubic feet, divide cubic meters by 35.23 (3.28 ft x 3.28 ft x 3.28 ft). You can also convert meters to feet before you multiply by dividing each measurement by 3.28.

Cut-Off Riser

Poly cut-off risers contain multiple sets of threads that can be cut-off to the desired height. Use a PVC pipe cutter, hacksaw, or utility knife to cut off a nipple section.

Make your cut at the top of the thread section. Teflon tape is not required on poly cut-off risers. See also Riser.

Cycle

A complete run of all stations programed to operate on an irrigation controller.

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Design Capacity

 The volume of water and the working water pressure available on site with which to design an irrigation system. The design capacity determines the number of sprinkler heads that may be in operation at the same time.

 

Diameter

In irrigation, diameter is used to reference two things:

1. The measurement across the circular opening of a pipe. Note that both Inside Diameter and (ID) and Outside Diameter (OD) are often referenced. This is especially important when choosing drip tubing as there are at least five different sizes that could be called "1/2 inch drip tubing" on the market.
2. The Diameter of Throw for full-circle spray nozzles, rotors, drip emitters, and micro spray caps. See also Diameter of Throw. 

Diameter of Throw

The average diameter of the area covered by a full-circle sprinkler operating in a wind-free environment.

Diaphragm

The diaphragm is a flexible rubber membrane inside an automatic irrigation valve, between the upper chamber of the valve and the smaller valve inlet (water supply). When the valve is closed, both the upper chamber of the valve and the valve inlet are filled with water. Since the upper chamber is larger, a greater suface area of the diaphragm is covered with water than on the inlet side. This water pressure differential keeps the valve closed.

When the solenoid is electronically activated, it releases water from the upper chamber above the diaphragm. This reduces the water pressure above the diaphragm and allows it to rise and open the valve. Water will now flow through the valve.

A spring inside the valve pushes against the back of the diaphragm, but it does not exert much force on the diaphram. It would stay closed without the spring. See also Valve.

Direct-Bury Wire

The most common direct bury wire for irrigation systems is multi-strand wire. Insulated, colored-coded wires are wrapped together in a black insulating jacket. Direct-bury wire is available in various wire thicknesses and number individual wires (called "condutors") bundled together.

When wiring irrigation valves with direct-bury wire, each valve gets one wire and all valves share one common wire. For example, If you have three valves underground in a valve box, you will need to run 4-strand direct-bury wire from the irrigation controller to the valves in the valve box. If you anticipate adding more valves in the future, install direct-bury wire with more strands. Use waterproof connectors when connecting wire to irrigation valves.

Less common are "two-wire" systems with a two-conductor wire to power all of the valves. See also Valve, Valve Box, and Two-Wire.

Distribution Tubing

See Micro Tubing.

Distribution Uniformity

This refers to how evenly water is distributed over an irrigated area. Distribution Uniformity (DU) is determined using a catchment test. Cups are evenly spaced over the area to capture the water as it is delivered by the irrigation system.

The most common method for determining DU is called the Low Quarter method. To determine the DU of an irrigation zone using this method, divide the average reading of the lowest one-quarter of catchments by the average reading of all catchments. Multiply that number by 100.The resulting percentage is your Distibution Uniformity.

A DU of 75% - 85% is excellent.

65% - 70% is good.

A DU below 65% is generally considered poor.

See also Irrigation Efficiency.

Double Check Valve Assembly

A Double Check Valve (or double check valve assembly) is a backflow preventer containing two positive-seating check valves assembled in series.  A ball valve or gate valve is installed at each end for isolation and testing of each check valve. Small ball valves, called test-cocks, provide locations for attachment of testing equipment.

The benefit of the double check valve is that it does not need to be installed above the highest head or pipe in the irrigation system. It can be installed underground in a valve box. See also Backflow Preventer.

Downstream

An irrigation term referring to pipe, fittings, sprinklers, etc. that are away from the water source in the direction of the water flow.

Drip Irrigation

Drip irrigation is a watering method which delivers water to plants slowly at the roots. It is also known as trickle or micro-irrigation. Where typical pop-up sprinklers spray water into the air and onto plants, drip irrigation systems combine flexible poly drip tubing and drip emitters (or drippers) to both conserve water and save money.

Drip systems are not affected by wind and will greatly reduce evaporation and runoff common with traditional irrigation systems. Drip irrigation is the perfect solution for raised beds, vegetable gardens, and potted plants.  See also Emitter, Barbed Fitting, and Poly Pipe.

Learn how to plan, design, and install your own Drip Irrigation System with our FREE online Drip Irrigation Tutorials.

Drip Regulator

See Regulator.

Drip Tape

Commonly used by commercial growers, drip tape is a thin-walled dripline with inline emitters pre-installed at preset spacings. The tape is flat and expands when filled with water. It is a great product for row crops and vegetable gardens. 

Drip tape fittings use a twisting mechanisim rather than compression or barbed fittings like conventional drip tubing.

Drip Tubing

Also called "Poly Tubing" or "Poly Pipe" it is a common term for Polyethylene pipe. a flexible, black tubing used for drip mainline and drip micro tubing. It is most commonly available in rolls of 100 or 500 feet. The inner diameter (ID) and outer diameter (OD) varies.

Common sizes are:

1/8" tubing (primarily used in nurseries)

1/4" micro tubing (most often used as lateral feeder lines off of the larger tubing below)

710 - .710" OD (Uses blue-ringed fittings)

700 - .700" OD (Uses black-ringed fittings)

620 - .620" OD (Uses green-ringed fittings). The Raindrip brand is 620 tubing. 

940 - .940" OD (Uses gray-ringed fitting)

Fittings used with poly pipe can be compression or barbed. See also Polyethylene, Compression Fitting, Barbed Fitting.

Dripper

See Emitter.

Dynamic Head

See Total Dynamic Head.

Dynamic Water Pressure

Also known as working pressure or operating pressure, the Dynamic Water Pressure is the measure of water pressure with the irrigation system running. The dynamic water pressure will drop below the static water pressure when the system is turned on.

With sprinkler systems, pressure is usually measured at the base or nozzle of a sprinkler.

To measure the dynamic water pressure of a drip system, install a compression tee in the mainline. Add a section of drip mainline tubing to the tee and a compression adapter with hose threads to the drip tubing. Attach a hose-threaded pressure gauge to the fitting. When you turn on the drip system, the gauge will give you a reading of that system's dynamic water pressure. Flow rate will, of course, affect dynamic water pressure. See also Static Water Pressure, Pressure Gauge.

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Elbow

An L-shaped fitting used in irrigation. to make a 90 or 45 degree turn in an irrigation or drainage line. Elbows (also called "Ells", "90s", or "45s") can be found in a variety of materials including PVC, polyethylene, galvanized steel, and copper. They may be threaded, slip, barbed or in cominations thereof.  

 

Electric Valve

See Valve.

Elevation

It is important to consider changes in elevation when designing an irrigation system. If a particular zone has high and low spots, the water pressure will vary at those locations. This is of particular concern with drip systems, which operate at lower pressure than most sprinkler systems. Water pressure is represented in Pounds per Square Inch (PSI).

 

Water Pressure changes .433 pounds per foot of elevation change.

 

For example:

1. Water pressure increases by 1 pound for every 2.3 feet of rise in elevation.
2. It decreases approximately 4 pounds with every 10 foot drop in vertical elevation. 

If a drip irrigation zone contains substantial changes in elevation, it is best to use pressure compensating emitters, as they will maintain the same output regardless of pressure fluctuations. The output of non-pressure-compensating emitters will fluctuate with changes in elevation and pressure. See also Pressure Compensating, Non-Pressure-Compensating

Elevation Gain

Water pressure gained as water moves to a lower elevation. Water pressure increases at a rate of .433 pounds per square inch (psi) for each foot of elevation loss.

Elevation Head

Also known as potential or static head, it represents the vertical elevation that water must be lifted from the water source to the highest irrigation sprinkler, drip emitter, etc. It is a measurement of pressure expressed in units of elevation (i.e. feet, meters).  .

The sum of the Elevation Head. Pressure Head, and Friction Head is equal to the Total Dynamic (or Hydraulic) Head. See also Total Dynamic Head, Pressure Head, Friction Head.

 

 

Elevation Loss

Water pressure lost as water moves to a higher elevation. Water pressure decreases at a rate of .433 pounds per square inch (psi) for each foot of elevation increase.

Emitter

Also called a dripper, an emitter distributes water droplets at a specified flow rate when used as part of a drip irrigation system. Emitters come in a variety sizes, styles, and flow rates. They have barbed or threaded bases. Barbed ends are either poked into 1/2" drip tubing or inserted into the end of 1/4" tubing. Threaded bases are screwed into micro tubing stakes and risers.

Drip Emitter Tubing  comes with emitters pre-inserted in the tubing. It can be purchased in both 1/2" and 1/4" sizes with emitters spaced from 6 inch to 3 foot intervals.

Inline Emitters  are use to create custom emitter tubing when used with 1/4" solid drip tubing.

Pressure Compensating Emitters distribute a consistent flow rate regardless of fluctuations in pressure.

Non-Pressure-Compensating Emitters will distribute varying flow rates as pressure fluctuates with elevation changes.

Staked Emitters sit on a spike and may distribute water in a spray or stream.

Multi-Outlet Emitters can be installed onto existing sprinkler rises as part of a sprinkler retrofit project. 1/4" tubing is installed on the emitter outlets and run to individual plants.

See also Emitter Tubing, In-line Emitter, Pressure Compensating, Non-Pressure-Compensating.

Emitter Tubing

Also called dripperline, emitter tubing has emitters injected into the tubing as it is extruded. The tubing comes with emitters evenly spaced from 6 inches to 3 feet on center. It is useful in row crops, vegetable gardens and evenly-spaced tree and shrub plantings. It is available in both 1/2" and 1/4" tube sizes.

Evaporation

The natural process of changing water into water vapor. As temperatures rise, evaporation increases. See also Transpiration.

Evapotranspiration

The combination of plant transpiration and evaporation, as water is converted to water vapor and moves into the atmosphere. Evapotranspiration (ET) rates are used to schedule the watering needs for specific crops. See also Transpiration and Evaporation.

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Faucet

See Hose Bibb.

Female Adapter

Adapters connect parts of unlike size, threads, or connection type. A female adapter has internal threads or slip fitting.

Female Hose Thread

See Hose Thread

Female Pipe Thread

See Pipe Thread.

Fertigation

Applying fertilizer to plants through an irrigation system. It is commonly used in drip systems with vegetable crops. Fertilizer is injected into the system so that the nutrients are mixed with water and delivered to all plants on that specific watering zone. Fertilizer is applied in small amounts early in the crop's season, as they begin to leaf out. The dosage is increased as the crop begins to produce fruit and nutrient requirements increase.  The application of fertilizer is decreased as plants near the end of their growth cycle.

FHT

FHT: Female Hose Thread

See also Hose Thread.

Filter

A filter contains a screen that is designed to remove particles from irrigation systems. Filters are critical components in a drip irrigation system. Drip emitters may clog if proper filtration is not provided. Typical screen mesh is 120, 150, and 200 mesh. The greater the number, the smaller the openings in the screen. 200 mesh is recommended for foggers (misters).

Fittings

The common name for parts that connects irrigation parts and pipe. These include elbows, tees, couplers, crosses, male adapters, female adapters, swivel adapters, control valves, reducers, bushings, street elbows. They may be threaded, slip, barbed, compression, or a combination thereof.

Flood Bubbler

See Bubbler.

Flow Control Valve

An in-line valve that allows a section of the watering zone to be turned off. This is especially handy in drip systems when watering raised flower or vegetable garden beds. Install a control valve for each bed. If a particular bed does not get planted, simply shut off the control valve until it is planted and ready to be irrigation.

 

Install small 1/4" flow control valves when adding drip irrigation to flower pots. The control valve allows you to adjust the flow to the pot or shut it off completedly if the pot is empty.

Flow Rate

The movement of water through pipe, fittings, valves and generally measured in Gallons per Minute (GPM) and Gallons per Hour (GPH). You will need to know the flow rate when planning an irrigation system. It is the key factor when determining the maximum number of zones or emitters per zone. Once you know your flow rate, you know the maximum amount of water available for your system. Keep that in mind when adding up the output (flow) of sprinklers or drip emitters that you are considering for your system.

To determine the flow rate out of your faucet (hose bibb, spigot, hydrant), read our tutorial on Determing Your Flow Rate.

FPT

FPT: Female Pipe Thread. See also Pipe Thread.

 

Friction Head

Friction Head (FH)  represents the friction loss as the water moves through valves, pipe, and fittings. Water velocity also creates turbulence which factors into the total friction loss.

It is used to determine the energy required to irrigate a given area. See also Total Dynamic Head, Elevation Head, Pressure Head.

Friction Loss

Represents the amount of pressure lost as water moves through valves, pipe, and fittings. Friction occurs as water comes in conatct with the inner walls of these materials and reduces the overall available water pressure in the system. Water velocity also creates turbulence which factors into the total friction loss. As velocity increases, so does turbulence.

Pipe material, length, and inside diamter all contribute to friction losses. These losses can be used to approximate the Dynamic Water Pressure of an irrigation system. See also Dynamic Water Pressure, Total Dynamic Head, Elevation Head, Pressure Head.

Funny Pipe

See Swing Pipe.

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Gate Valve

A manual on/off valve designed to be used in either the open or closed position and not meant to control or regulate flow in an irrigation system. It is best used as a back-up shut-off valve in case of line breaks. The internal mechanism, as the name implies, is a "gate" which slides up and down as the handle is turned and the valve is opened or closed.

Gear Drive Sprinkler

See Sprinkler.

Globe Valve

A common style of irrigation control valve, the globe valve is an inline valve that requires a backflow prevention device. It is usually installed underground in a valve box in groups of 3 to 4 valves.

It features an inlet on one side of the valve and outlet on the other side. A similar valve is the Angle Valve in which the inlet comes up though the bottom of the valve. Globe and angle valves have an internal diaphragm that presses down on the inlet side in order to close the valve. Globe valves have somewhat higher friction losses than angle valves. See also Valve, Friction Loss, Backflow Preventer.

Goof Plug

Also called mistake plugs, goof plugs are used in drip irrigation to plug up small holes in mainline drip tubing. They are also used as end caps in 1/4" drip micro tubing. It is always good to keep a handful of goof plugs on hand.

GPH

GPH: Gallons Per Hour. See also Flow Rate.

GPM

GPM: Gallons Per Minute

When designing a sprinkler system is it important to know your flow rate as sprinkler heads have varying GPM outputs and requirements. Add up the output of all your proposed sprinklers (in GPM) to determine the total allowable with your given flow rate. See also Sprinkler,  Flow Rate.

Gravity Drip Irrigation

A drip irrigation system that is that gravity fed. Water is placed into a raised container so that gravity will provide enough pressure to cause water to flow down to the drip emitters. Drip tape and non-pressure-compensating emitters are best used with a gravity fed system because both can operate at very low flow rates with low pressure. See also Drip Tape, Non-Pressure-Compensating.

Gravity Flow

See Gravity Drip Irrigation.

Gray Water

Household wastewater (wash water) coming from sinks, washing machines, shower and bathtubs. It does not contain sewage and is some times reclaimed and recycled for use in irrigation systems.

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HDPE

See High Density Polyethylene.

Head

See Pressure Head, Sprinkler.

Head Loss

See Friction Loss, Friction Head.

Head Spacing

The space between sprinkler heads. See also Head-to-Head Coverage.

 

Head-to-Head Coverage

The concept of spacing sprinklers so that each sprays water to the base of the nearest sprinker (or sprinklers). Most sprinklers will perform best with head-to-head coverage. Designing for head-to-head coverage will ensure that you have no dry spots due to lack of water. See also Sprinkler.

High Density Polyethylene

(HDPE) A black plastic used to make irrigation pipe, valves, and fittings.

Hole Punch

A device used to poke a hole into solid drip poly tubing for the insertion of drip emitters (drippers). See also Poly Pipe, Emitter.

Hose Bibb

Also known as a spigot, faucet, or hydrant, a hose bibb is a manual valve attached to the main water line and found at most homes and some commercial buildings. It has male hose threads and is degined to accomodate the connection of a garden hose. 

Hose Thread

Officially called "Garden Hose Thread" (GHT), hose threads are found on garden hoses and many irrigation parts and adapter fittings. Generally referred to as "3/4" hose threads" the outer diameter is 1.0625 inches and has a pitch of 11.5 tpi (threads per inch). Hose threads are NOT the same as pipe threads and should never be screwed into pipe threaded fittings.   

Male hose threads are found on the outside of a fitting and thread into female hose threads.

Female hose threads are found on the inside of a fitting and accept male hose threads.

Hose threads do not require Teflon tape or pipe dope (like pipe threads), just a hose washer. If you find a water leak with hose threads, it is most likely a worn hose washer. It may be time to replace it. Hose washers are found inside fittings with female hose threads. See also Pipe Thread, Adapter, Swivel, Hose Washer, Teflon Tape

Hose Washer

Rubber gasket found inside fittings with female hose threads that makes a water-tight seal. See also Hose Thread.

HT

See Hose Thread.

Hydrant

Also called a yard hydrant or garden hydrant, it is is a manual valve attached to the main water line. It has male hose threads and is degined to accomodate the connection of a garden hose. See also Hose Bibb, Hose Threads.

Hydro-Zone

The concept of planning your irrigation watering zones based on plant needs and micro climate (shade, sun, etc.).  Hydro Zones include tree zone, shrub zone, sunny zone, shade-plant zone, succulent zone, etc. Degining an irrigation sytem with hydo zones allows you to modify the water distribution to plants of similar sizes, water needs, sun exposure etc.

 

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ID

Abbreviation for Inside Diameter of pipe.

Impact Drive Sprinkler

See Sprinkler.

In-Line-emitter

There are two types of inline emitter (or inline dripper):

1. Emitters that are inserted into drip tubing as it is extruded to make a drip irrigation product call emitter tubing or dripperline.

2. Emitter with barbed ends that can be used to make custom-sized emitter tubing

• Make your own 1/4" emitter tubing. You to control the spacing. Cap the end of the 1/4" tubing with a goof plug.
• Add a little more water where needed. Cut the 1/4" tubing and insert the emitter into each end.

See also Emitter Tubing.

Injectors

Used to inject liquid fertilizer and other nutrients into a drip irrigation system. It actually a vacuum that sucks the fertilizer into the irrigation system. A pressure differential between the inlet and outlet of the injector creates a vacuum inside the fertigation device creating the suction.  Fertilizer is then "injected" into the drip system.  See also Fertigation.

Inrush Current

 The current required to initially open the solenoid of an electric irrigation valve. See also Valve.

Internal Manual Bleed

Used to manually turn on an automatic valve. a bleed valve is located on or near the top of the valve. It can be a small screw, a lever, or built into the solenoid. An internal bleed will keep the water inside the valve and empty it into the downstream side of the valve. See also Bleed Valve.

Irrigation Efficiency

Irrigation Efficiency differs from Distribution Uniformity (DU). While DU is a measurement of the how evenly distributed the water coverage is in a specific a watering zone, Irrigation Efficiency refers to how well matched the amount of water applied is to the actual needs of the plants being watered. For example if a row crop needs 30” of water per year and the system is programmed to apply an amount close to 30",  the irrigation efficiency is considered high. However, if system applies 50” per year to the same row crop, the DU may be high, but the irrigation efficiency is considered very low. See also Distribution Uniformity.

Irrigation Schedule

Refers to the programming of an irrigation controller. The irrigation schedule accommodates the needs of various plant types and locations on a property. For example, large trees may require the slow, deep watering of a drip system for an hour or more. Trees may only need to be watered once per week (or less). At the same time, a lawn with a conventional sprinkler system, may need to be watered twice a day during the hot summer months.

Start times are also important. If you can water during the early or late parts of the day, less water will be lost to evaporation. Clay soils are more compacted than loamy or sandy soils. Capillary action between clay particles bind the soil and may cause irrigation water to pool and run-off. In that case, you would schedule frequent waterings for short durations in areas where the soil is predominantly clay.

All of these variations can be accommodated given a little thought and planning and the proper irrigation controller. See also Controller

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Jockey Pump

Used in a multiple-pump irrigation system, a jockey pump provides for the following:

1. If the flow requirement from one pump is not sufficient for the irrigation system, the jockey pump can operate alongside one of the main pumps and provide the additional flow needed.
2. The jockey pump can operate on its own and provide water to select areas of the irrigation system that do not require the full flow of the main water pump.
3. It can generate smaller flow than the main pumps when a slower application of water is required than that supplied by one of the main pumps. This includes deep, slow flood irrigation or providing water to garden hoses
4. Reduces the chances of water hammer by maintaining water pressure in the irrigation main. That way, water is never pumped into empty main lines. 

 

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Kinetic Energy

With respect to irrigation, Kinetic Energy (KE) is the energy present in a column of water as it moves through a pipe. It is the energy that creates a water hammer.  A Water Hammer Arrester can be installed to absorb the kinetic energy and prevent water hammer. See also Water Hammer, and Water Hammer Arrester.

KPa

A metric unit of measuring pressure. One KPa equals one thousand Pascals. 101.325 KPa equals one atmosphere.

One Pascal equals a force of one Newton per square meter. A Newton is the force required to give a 1 kilogram mass an acceleration of 1 meter per second. Since the Pascal is a very small pressure, KiloPascals (kPa) are more commonly used.

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Labyrinth

Some emitters contain a labyrinth inside which dissipates the water energy by means of the
built-in channel obstacles along its length. The obstacles in the labyrinth channel create a turbulent flow which maintains the specified discharge rate and helps prevent clogging. See also Emitters.

Laser Tubing

A laser-drilled micro tubing with holes at preset spacings. It is not as precise as drip emitter tubing. See also Emitter Tubing.

Lateral Line

Used to describe branch lines in an irrigation system, usually run from the main supply line in a particular zone. It is run from the main line to the drip emitters or sprinklers, and is not under constant pressure. Lateral lines are only under pressure when the zone is running.

 

LCD

Liquid Crystal Display, often found in irrigation controllers. See also Controllers.

Liters Per Hour

A metric measurement of water flow, often found on flag emitters. See also Flow Rate, Emitter.

Liters per Minute

A metric measurement of water flow. See Flow Rate

Looped Circuit

Generally used in mainline applications, a looped circuit is one that closes back onto itself and provides water to valves from more than one route.

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Main Line

With standard irrigation systems using PVC pipe, the main line (or main) usually refers to the pressurized pipe that carries water from the water source (point of connection) to the irrigation control valves.

With drip irrigation, the 3/4" or 1/2" poly supply line is often referred to as the mainline or "drip main line". See also Drip Tubing.

Male Adapter

Adapters connect parts of unlike size, threads, or connection type. A male adapter has external threads on one end and a slip fitting on the other. See also Female Adapter.

 

Male Hose Thread

See Hose Thread.

Male Pipe Thread

See Pipe Thread.

Manifold

A grouping of irrigation valves, often in a valve box, that send water to multiple watering zones. See also Valve. Main Line.

Manual Bleed Lever

See Bleed Valve.

Marlex

"Marlex" is a brand name for High Density Polyethylene (HDPE) commonly used in irrigation systems to create swing joints. Marlex has a slippery or oily feel. The threads won't stick when making adjustments for swing assemblies. Marlex fittings are not required to be leak-free, and should not be installed under constant pressure. The only time a Marlex fitting should be pressurized is when the sprinkler system is running. A little dripping or leaking while the system is running is OK. Teflon tape is not required on the threads of Marlex fittings. See also Marlex Elbow, Swing Joint, Swing Assemby, High Density Polyethylene.

Marlex Elbow

A street elbow made from high-density polyethylene (HDPE) and used to make swing joints and swing joint assemblies. See also Swing Joint, Swing Assemby, High Density Polyethylene.

Master Valve

Master valves are electric valves used in irrigation systems to control main line water flow to a manifold (group of irrigation valves). The master valve is wired to the irrigation controller and is installed upstream from the manifold on the mainline. It is activated just before the irrigation zone valves. Since it is turned off when the system shuts down, it will reduce water loss if there is a leak in one of the zone valves. This is convenient if manifold valves need repair as the master valve shuts off water supply to the manifold.

See also Valve. Main Line, Manifold.

Matched Precipitation Rate

When all the sprinkler heads in an irrigation zone have similar precipitation rates, that zone has matched precipitation rates. For example, when selecting nozzles for pop ups, the precipitation rate for the full circle (360°) nozzle should be roughly four times that or the same nozzle in a quarter spray (90°). The half circle (180°) should have a precipitation rate that is roughly double that of the quarter spray.

To avoid areas of over or under watering within a zone, be sure to match the precipitation rates of the nozzles, rotors, impact heads, etc.

See also Precipitation Rate. Sprinkler, Nozzle.

Meter Wrench

A T-handled tool for opening and closing residential water meters. The wrenches are long-handled since the meters are underground in valve boxes.

MHT

Male Hose Thread. See also Hose Thread.

Micro Irrigation

See Drip Irrigation.

Micro Spray

Micro spray covers a category of spray caps, bases, one-piece, and adjustable sprayers that are small and designed to operate with drip irrigation systems. They can be used in flower and vegetable gardens and landscapes when you need to water a large area. Caps and bases are combined for a variety of patterns, diameters, and flow rates. They are color coded to indicate pattern and flow rate. See also Micro Sprinkler.

Micro Sprinkler

Micro sprinklers (also called Rotary Micro Sprayers or Spinners) are a rotating mini sprinkler that is installed on drip tubing. They operate at low pressure (20 psi is ideal), and can cover an area up to 15 feet in diameter. See also Micro Spray.

Micro Tubing

Sometimes called "Spaghetti Tubing", 1/4" micro tubing can be used as main line for small deck/flower-pot installations, but is more often used as a lateral line coming off a 1/2" poly supply line (main line).The micro tubing carries water to emitters (drippers), and micro sprays. Also referred to as "Distribution Tubing" it is available in polyethylene or, the more flexible, vinyl. See also Drip Tubing, Lateral Line, Micro Spray,Micro Sprinkler, Main Line.

Mist Irrigation

Uses misters or foggers, installed on a drip irrigation system, to create a misty spray or fog. It is recommended that you used drip regulators of 45 psi or higher in order to generate finer water droplets. See also: Regulator.

Mistake Plug

See Goof Plug

Moisture Sensor

See Soil Moisture Sensor.

MPT

Male Pipe Thread. See also Pipe Thread

Mulch

Mulch is a 2 - 6 inch layer of dried material that is spread onto the soil near plants. Common mulch materials include shredded bark and dried leaves. Used with drip irrigation systems, a layer of mulch will both extend the life of drip tubing and components and help retain water in the soil. 

Multiple Start Times

A common feature found in irrigation controllers that provides for a zone to be watered at multiple times on the same day. This is helpful when shallow rooted plants (like grass) are planted during hot summer months and require frequent waterings.

Clay soil particles are tightly bound and can easily cause run-off. Multiple start times allow you to prevent run-off by watering clay soils more often but for shorter durations, giving the water time to soak in before flowing away. See also Controller.

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Nipple

See Riser.

Non-Compensating

See Non-Pressure-Compensating.

Non-Potable Water

Water that is not suitable for drinking.

Non-Pressure-Compensating

Non-Pressure-Compensating Emitters. The output will vary with changes in elevation and pressure. These emitters are best used where the watering zone is level. Some non-pressure-compensating emitters are used with gravity-fed drip systems. They operate best at lower pressures. Recommended Pressure for most non-p-c emitters: 15-20 psi. See also Emitter, Pressure Compensating.

 

Nozzle

The orifice attached to the top of a sprinkler that determines the pattern and the distance of the spray that comes out of the sprinkler. Many nozzles require (or come with) a small filter that drops down into the sprinkler. The flow rate for the sprinkler is often determined by the nozzle size and pressure at the sprinkler head.

 

Nut Driver

Commonly used to screw in a hex nut, a 5/16" nut driver is the perfect tool for screwing threaded micro spray fittings in to stakes and risers. See also Micro Spray.

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OD

Abbreviation for Outside Diameter of pipe.

Operating Pressure

See Dynamic Water Pressure.

Orifice

The opening in a valve, pipe, tubing, fitting, nozzle, spray nozzle, or micro spray fitting. It determines the flow rate through that part.  

Outer Diameter

See OD

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Pascal

A metric unit of measuring pressure. It equals a force of one Newton per square meter. A Newton is the force required to give a 1 kilogram mass an acceleration of 1 meter per second. Since the Pascal is a very small pressure, KiloPascals (kPa) are commonly used. One KPa equals one thousand Pascals. 101.325 KPa equals one atmosphere.

The Pascal is now widely used. This is the S.I. unit, and equals a force of one Newton per square metre (in turn, a Newton is the force required to give a 1 kilogram mass an acceleration of 1 metre per second per second.) The Pascal is quite a small pressure, so we often use KiloPascals (kPa), equal to one thousand Pascals. 101.325 kPa equals one atmosphere.

PE

Polyethylene. See also Polyethylene.

Percolation Rate

The rate at which water moves through soil.

pH

A measure of acidity or alkalinity.

Pig Tail

A three-pronged plug-and-cord used with irrigation controllers that have internal transformers. The end of the cord contains three wire strands that are connected to the transformer inside the controller. The cord is then plugged into an electrical outlet. This eliminates the need to hard-wire the controller to the power source. See also Transformer, Controller.

Pipe Dope

A chemical sealant (sometimes containing Teflon) that is used to seal pipe-threaded fittings. It has the consistency of a thick paste and is commonly white or yellow. It not only creates a water-tight seal, but it also helps the fittings thread together more easily. 

 

Pipe Thread

The common term for National Pipe Thread (NPT). Pipe threads require Teflon tape or pipe dope to create a water-tight seal. Do not thread together pipe threads and hose threads. See also Teflon Tape, Pipe Dope, Hose Thread.

POC

See Point Of Connection. 

Point of Connection

The place where an irrigation system connects to the main water supply. It refers to any water supply including, City-metered water, lake, pond, well, irrigation ditch, rain-barrel, or irrigation ditch.

Poly Pipe

See Drip Tubing.

Poly Tubing

See Drip Tubing.

Poly Vinyl Chloride

(PVC) A type of plastic used to make pipe and fittings for irrigation. It is most often white but is also found in gray, brown, tan, and purple. These colors represent either the type of water being transported (e.g. purple represents reclaimed water) or pipe thickness (gray represents "Schedule 80" pipe thickness).

It can become brittle with prolonged exposure to sunlight, so it is commonly buried. See also Class 200, Schedule 40, Schedule 80.

Polyethylene

(PE) A very common plastic used for manufacturing irrigation tubing and fittings. High Density Polyethylene (HDPE) is the type of Polyethylene used to make pipes and fittings for water. See also Poly Vinyl Chloride.

Pop-Up Sprinkler

See Sprinkler.

Potable Water

Water that is safe for drinking. 

Precipitation Rate

The rate at which a sprinkler head delivers water to an area, measured in inches per hour or millimeters per hour. It is important to ensure that water distribution is as even as possible in a given area. See also Matched Precipitation Rate, Sprinkler, Nozzle.

Pressure

With respect to irrigation, pressure is a measurement of the force of water within an irrigation system or main line, usually expressed in pounds per square inch (PSI). It is the force that moves (or has the potential to move) water through valves, pipes, fittings, sprinklers and emitters. 

Static Pressure is measured when the system is closed and no water is flowing through it.

Dynamic Pressure is measured when the system is open and water is flowing through. Flow and pressure affect each other.

Drip irrigation operates at pressure generally lower than most household water pressure.

See also Dynamic Water Pressure, Static Water Pressure, Regulator, Main Line.

Pressure Compensating

Pressure Compensating Emitters. The output will not vary with changes in elevation and pressure. They deliver the stated gph (gallons per hour) even if pressures range from 10-50 psi. These emitters are best used with elevation changes. They are self-flushing to reduce clogging. See also Emitter, Non-Pressure-Compensating.

Pressure Gauge

A device used to measure water pressure. Inexpensive gauges can be purchased at hardware and home improvement stores. Attached the gauge to a hose bibb or faucet to measure static water pressure. For instructions on measuring dynamic pressure of a drip system, see Dynamic Water Pressure. See also Static Water Pressure.

Pressure Head

Pressure Head (PH) represents the pressure required to operate the drip emitters or sprinklers in an irrigation system. It is one component used to determine the Total Dynamic head, the total energy required to irrigate a given area. See also Total Dynamic Head, Elevation Head, Friction Head.

Pressure Loss

Pressure is lost as water moves through an irrigation system due to friction/turbulence as it comes in contact with the inner walls of pipe and fittings. Pressure also decreases as elevation increases. These forces must be calculated in order to determine the dynamic (operating) water pressure that you have to work with when designing your system. See also Friction Loss, Friction Head, Elevation Head, Pressure Head, Total Dynamic Head, Friction Head, Dynamic Water Pressure, Static Water Pressure, Pressure Gauge.

Pressure Rating

Corresponds to a thickness of irrigation pipe or fitting and the recommended maximum internal pressure that can be exerted inside the pipe or fitting.

Pressure Regulator

A device that lowers water pressure on the downstream side and maintains a constant operating pressure. Regulators are commonly used in drip irrigation applications as drip tubing and fittings are usually rated to operate at pressures lower than most household water systems. Always install a regulator after a valve and filter. They are not designed to be operated under constant pressure.

Pressure Vacuum Breaker

See Backflow Preventer

Program

The process of entering watering information into a controller (or the information itself). The program will include the days to water, watering start times, and watering duration for each zone. See also Irrigation Schedule, Multiple Start Times, Controller, Zone.

PSI

Pounds per Square Inch. A measurement of water pressure. One atmosphere is approximately 15 psi. See also Pressure, Dynamic Water Pressure, Static Water Pressure, Regulator.

PT

See Pipe Thread

Pump

A mechanical device used to move water. A centrifugal pump is commonly used for irrigation systems.

Common Pumps Used in Irrigation and Drainage Applications:

Centrifugal Pump: Uses centrifugal force, has an internal impeller.Includes multi-flow, multi stage, radial flow, verticle turbine, and booster pumps.

Jockey pump A small pump used in  multi-pump systems.

Submersible (sump) pump Pump and motor are both submerged under water. Commonly used in drainage systems.

Pump Efficiency

The ratio of the water power produced by the pump to the power used by the pump to create that water power. It is expressed as a percentage or decimal.

Pump Start Circuit

A feature on many irrigation controllers that starts the pump which provides the water pressure to the irrigation system. It works in conjunction with a pump start relay. See also Controller, Pump, Pump Start Relay.

Pump Start Relay

The pump start relay is an electronic device that uses a signal current from the irrigation controller to activate a pump to provide water to the irrigation system. It is only needed for irrigation systems using a pump to pressurise the irrigation system.

See also Controller, Pump, Pump Start Circuit.

PVC

See Poly Vinyl Chloride.

PVC Pipe

Irrigation pipe made from PVC (poly vinyl chloride). See also Poly Vinyl Chloride, Class 200, Schedule 40, Schedule 80.

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Quick Coupling Valve

Often made of brass, it is an underground valve that is under constant pressure and designed to provide a quick water connection. A hollow, tubular coupler key is inserted in the quick coupler and turned to lock it into place. A garden hose is often connected to the key.

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Radius of Throw

The distance from the sprinkler head to the farthest point of spray. Used in specifications for nozzles and spray heads with circular spray patterns. See also Nozzle.

Rain Delay

A feature on an irrigation controller which allows the user to delay watering for a period of time. The controller resumes its watering schedule once the delay period has ended. See also Soil Moisture Sensor, Rain Sensor, Rain Sensor Bypass, Controller.

Rain Gauge

A device used to measure rainfall. It can be as simple as a graduated cylinder on a stake or as sophisticated as a wireless, digital, self-emptying device with memory and temperature readings. Electronic sensors can be connected to irrigation controllers and suspend watering as needed. See also Rain Sensor, Controller.

Rain Sensor

A micro-switch weather-sensing device which measures rainfall. The sensor connects directly to the irrigation controller and stops the watering cycle when precipitation provides sufficient water for plant growth. See also Rain Gauge, Soil Moisture Sensor, Controller.   

Rain Sensor Bypass

A feature on some irrigation controllers which allows the user to bypass a rain sensor (or soil moisture sensor) and use the controller.  See also Rain Sensor, Soil Moisture Sensor.

Rain Shut-Off Device

See Rain Sensor, Rain Sensor Bypass.

Rain Switch

See Rain Sensor

Rainbucket

See Rain Sensor.

Raindrip

A retail brand of drip tubing with an outside diameter or .620 inches. This differs from other main line drip tube sizes. See also Poly Pipe.

Reduced Pressure Backflow Preventer

See Backflow Preventer.

Reducer

Also called a "reducer bushing", this fitting is used to increase or decrease pipe/fitting size. They come in threaded, slip or a combination thereof. The bushing threads or slips into the larger fitting or pipe, allowing it to accommodate the smaller size.

Regulator

See Pressure Regulator.

Riser

Also called a nipple, a riser is a section of pipe which usually has male pipe threads on each end. It is often threaded into the bottom of a sprinkler and into a threaded fitting below ground. They are available in a variety of materials. Some have cut-off sections which allow you to fine tune the height of the sprinkler when installing. See also Cut-Off Riser, Sprinkler.

Root Depth

See Root Zone.

Root Zone

Also called the "root depth" it is the area where most of a plant's rooting activity takes place. It is important to understand the pattern and depth of a plant's root zone when irrigating as water and nutrients must penetrate into this zone for the plant to obtain the greatest benefit.The maximum root zone can be affected by soil moisture, compaction, and profile.

Rotary Spray

A micro sprinkler that distributes large droplets of water and is best used for coverage of large areas (up to 15 feet).

Rotor Sprinkler

A gear-driven sprinkler head. See also Sprinkler.

Run Time

The length of time that a watering zone, or entire program, runs on an irrigation controller. See also Controller.

Runoff

Water that does not permeate the soil and instead flows away from the irrigated area. Runoff also occurs when sprinklers over spray planted areas an hit hard surfaces like concrete or pavement.

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Schedule 40

A PVC pipe classification (often written as SCH 40 or SCHED 40), commonly used for main line water pipes. Schedule 40 pipe is thicker than Class 200 and can withstand higher water pressure. The "schedule" number is not a specific measurement but rather a designation representing the reletive wall thickness of the pipe and water pressure rating (psi) for that pipe.  For additional classifications of irrigation pipe  see Shedule 80 and Class 200.

Schedule 80

A PVC pipe classification (often written as SCH 80 or SCHED 80), commonly used for risers in shrub areas, where the riser extends above ground. Schedule 80 pipe is very thick and usually gray in color. The psi rating for Shedule 80 PVC pipe ranges from 230-850 psi. The "schedule" number is not a specific measurement but rather a designation representing the reletive wall thickness of the pipe and water pressure rating (psi) for that pipe. For additional classifications of irrigation pipe  see Shedule 40Class 200. and

Seasonal Adjustment Switch

A feature on some irrigation controllers, it is used to increase or decrease the percentage of water applied by the entire system activated buy the controller. A Seasonal Adjustment Switch allows you to make a global run-time change without
re-programming the entire controller. It is best to initially program your controller with mild seasonal conditions in mind. This way you can simply increase the watering percentage in hot summer months and decrease it in the cooler fall months. Couple this with a weather sensor and your irrigation programming is effortless and nearly hands off. See also Controller, Rain Sensor, Soil Moisture Sensor.

Shrub Adapter

An adapter fitting that attaches to a 1/2" riser and accepts a spray nozzle. The riser stands above ground and often extends above the shrub to provide for adequate spray coverage.   It is used in ground cover and shrub areas.

Shrub Body

See Shrub Adapter

Shrub Sprinkler Head

See Shrub Adapter.

Shut-Off Valve

Generic name for a manual valve used to shut off the supply to an irrigation system. Usually a ball valve or gate valve, shut-off valves are installed on the main line near the main point of connection. See also Main Line, Valve.

Siphon

1. Also called a "siphon tube" or "overbank siphon", it is simply a bent tube that is used to siphon water from an irrigation ditch to the field on the other side (over the bank). The water in the irrigation ditch is at a higher elevation than the field.

2. Also known as a "back siphon" it is an undesirable siphon effect that may be caused when a break on a lower main line pipe pulls water back through the pipe from a higher location and creates a back flow. See also Backflow Preventer.

Slip

A Slip PVC fitting differs from a threaded fitting in that  it has no threads. The inside walls are smooth. The fitting is slightly larger than the pipe that fits into it. Solvent weld glue is applied to both the pipe and the slip fitting before the pipe is "slipped" into the fitting. Regarding terminology, an elbow that has two slip ends is called a "slip elbow". An elbow that has a slip end and a thread elbow is called a "slip-thread" elbow. See also Poly Vinyl Chloride (PVC)

Soil Moisture Sensor

Used with an irrigation controller to monitor soil moisture and prevent watering when irrigation is not needed. Soil moisture sensors are installed in the soil and set to a soil moisture threshold. If soil moisture is above this threshold the irrigation valve is bypassed until the soil moisture is below the threshold. See also Controller, Rain Gauge, Rain Sensor, Rain Sensor Bypass.

Solenoid

An electromagnet that is an integral part of an irrigation control valve. It is wired to an irrigation controller and facilitates the opening and closing of the valve. It operates at 24 Volts AC to pull a small plunger up from inside the valve. That action allows water to flow in over the internal diaphragm and open the valve. See also Valve, Controller, Diaphragm.

Spaghetti Tubing

See Micro Tubing

Spider Bubbler

A stream bubbler that sprays individuals streams of water in full circle, half circle, and end strip patterns. It is screwed onto a half inch riser and is good for watering trees and shrubs..

Spigot

See Hose Bibb.

Spinner

See Rotary Spray

Spray Head

See Sprinkler.

Sprinkler

Also referred to as a "sprinkler head" or simply a head. A sprinkler is a watering device that sprays water in fine or stream sprays when the irrigation system is under pressure. Sprinklers come in many sizes, shapes, and distribution types. Most sprinklers have removable or adjustable nozzles that control the pattern and distance of the spray that comes out of the sprinkler.

Some common sprinkler types:

Gear Drive Sprinkler (or Rotor)- A gear box drives the smooth movement of this higher-end sprinkler.

Impact Drive Sprinkler - A spring-loaded arm is pushed by the stream of water exiting the sprinkler nozzle. This impact moves the adjustable sprinkler in a circular pattern.

Spray Head  - A stationary spray head with a fixed nozzle attached to the top. Common in shrub applications.

Valve-in-Head   Each sprinkler has a control valve integrated into the design. These large sprinklers are often used in golf course applications.

Pop-Up Sprinkler    A below-ground sprinkler that pops up when pressurized. It has a fixed nozzle attached to the top. Common in turf (lawn) applications.

See also Nozzle, Diameter of Throw, Head-to-Head Coverage, Riser, Cut-Off Riser, Shrub Adapter, Bubbler

Square Spacing

Method of sprinkler layout where sprinklers are placed in a square pattern, directly opposite each other. This spacing can create dry areas if patterns do not overlap completely. Triangular spacing is often preferable to square spacing. See also Triangular Spacing, Head-to-Head Coverage, Nozzle, Sprinkler.

Static Head

See Elevation Head

Static Water Pressure

Water pressure that is measured when the system is closed and no water is flowing through it, as opposed to Operating (or Dynamic) Water Pressure.. Static Water Pressure is easily measured with a simple hose-thread pressure gauge found at most hardware and home improvement stores. Simply screw the gauge onto a hose bibb and open the faucet all the way. Read the pressure on the gauge. See also Pressure, Dynamic Water Pressure, Pressure Gauge. 

Station

A station is a single circuit on an irrigation controller. It contains the watering schedule run-time information for an electric solenoid valve. The station corresponds to a watering zone, which may be a group of sprinklers or a drip irrigation system. See also Controller, Zone.

Stream Bubbler

See Bubbler.

Street Elbow

An irrigation fitting. A Street Elbow has male threads on one side and female threads on the other. See also Fittings.

Subsurface Drip Irrigation

A method of placing drip emitter tubing (dripperline) underground and applying water directly to the root zone. Most emitter tubing is NOT designed to be buried under ground. Root intrusion can be a problem when burying drip tubing. Check with the manufacturer of the tubing before considering installing it under the soil. See also Emitter Tubing, Poly Tubing, Emitter.

Surge Pressure

The pressure caused when water stops suddenly in a pipe. Also called water hammer. For more details see Water Hammer.

Swing Assmbly

Swing assemblies protect sprinklers from damage. They provide flexibility so that pipes or risers do not break when a sprinkler head is run over or stepped on. Pre-assembled swing assemblies make it easy to place sprinklers precisely where you want them. See also Swing Joint, Marlex Elbow.

Swing Joint

A flexible joint made from threaded Marlex elbows and threaded PVC fittings. The threaded elbows are designed to take the impact from foot traffic. If the sprinkler is accidentally kicked, the threads allow the head to move without breaking. Swing joints also allow for fine-tuning of the final placement of the sprinkler head, without the need to cut and glue PVC pipe. See also Swing Assembly, Sprinkler, Marlex Elbow, Riser.

Swing Pipe

Sometimes called "funny pipe", swing pipe is a flexible irrigation pipe that works at high pressure (up to 80 psi). It uses barbed fittings and requires no glue. Swing pipe is an ideal solution for high-traffic areas where vehicle or foot traffic may damage sprinkler heads. See also Swing Assembly,Swing Joint, Sprinkler, Marlex Elbow, Riser.

Swivel

An irrigation adapter fitting with a female hose thread connection. A hose washer is required to make a water-tight seal.

System Water-Budgeting Switch

See Seasonal Adjustment Switch.

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Take-Off List

A list of materials needed for a project. It facilitates pricing and ordering parts. To create a take-off list., write down the names of all the potential fittings and pipes that you may need for the project.   Walk around the location and mark down the number of fittings and pipe sections needed. Total the parts and pipes. You are now ready to price out and order your materials.

Tee

A T-shaped pipe fitting used to create a branch (or lateral) line from another. They come in a variety of materials and connection styles. See also Fittings. 

Teflon Tape

A non-adhesive tape (made of Teflon non-stick material) that is used to create a water-tight seal with pipe threaded fittings. It is tightly wrapped in a clockwise motion 3-4 times around the male pipe threads. Male and female fittings are then threaded together.

Threaded Fitting

See Hose Thread, Pipe Thread.

Thrust-block

A poured-in-place concrete block used to support water pipes and keep them from moving when pressurized. This can be especially important with high-volume high-pressure water lines. Forces at elbows (where the water is changing direction) can cause the pipe to move. Over time, this movement will weaken pipe joints and may cause them to fail.

Timer

See Controller.

Total Dynamic Head

Also referred to simply as Total Head, it is the total energy required to irrigate a given area. Total Dynamic Head is calculated as follows:

TDH = EH + PH + FH

TDH = Total Dynamic Head (ft)

EH = Elevation Head & represents the vertical distance that water must be lifted. Also called Static Head.

PH = Pressure Head & represents the pressure required to operate the drip emitters or sprinklers in an irrigation system

FH = Friction Head & represents the friction loss as the water moves through valves, pipe, and fittings. Water velocity also creates turbulence which factors into the total friction loss.

These are used to determine the energy required to irrigate a given area. By considering all factors, efficient systems can be designed so that all sprinklers and emitters get the proper flow of water at the required pressure. See also Elevation Head, Pressure Head, Friction Head.

Total Static Head

See Elevation Head

Transformer

Transformers for irrigation controllers convert electrical energy from 100 to 24 volts. Outdoor Controllers have an internal transformer that is protected from the elements. An electrical cord (or Pig Tail) is wired to the transformer. Indoor controllers use external controllers. The transformer itself is plugged into the electrical outlet. the wires at the other end are connected to the controller. See also Controller, Pig Tail.

Transpiration

The loss of water by a plant through its leaves, flower parts, stems, etc. Transpiration makes up about 10 percent of the moisture found in the atmosphere. See also Evaporation, Evapotranspiration.

Triangular Spacing

The method of staggering the spacing of sprinklers so that they form a triangle pattern. This creates a spray overlap that provides the most efficient coverage of the irrigation area. See also Square Spacing.

Trickle Irrigation

See Drip Irrigation.

Turbulent Flow

Turbulent flow is created in pipes as a function of the interior roughness of the pipe. Turbulence creates "eddies" in the water which adds to the friction and creates a loss in pressure. The internal roughness and consquential turbulent flow is most significant in smaller diamerter pipes due to the increase friction loss. See also Friction Loss, Dynamic Water Pressure, Total Dynamic Head, Elevation Head, Pressure Head.

Two-Wire

A wiring method for irrigation systems that employs a two-conductor wire to power all of the valves. A decoder is connected to each valve. The decoders read the digital signals sent from the irrigation controller to open and close the valves.This eliminates the need for commonly-used multi-strand wire. It is also easier to add valves on to a two-wire system as any new valve is simply connected to the existing two wires. See also Direct Bury Wire, Controller.

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Uniformity

See Distribution Uniformity.

Union

A three-piece pipe fitting, similar to a coupler. The difference is that a union can be taken apart again if needed. It consists of three parts: two threaded sections that are attached to two lengths of pipe, and a threaded ring that joins the two. 

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VAC

Volts Alternating Current. Most irrigation controllers operate on 24 VAC and send 24VAC to the electric control valves in the field. See also Controller, Valve, Transformer.

 

Valve

A manual or electric irrigation device used to control the flow of water. These valves fall into two main categories:

 

1. Shut-Off Valves. Generally  installed on the main water supply to control the flow of water to the irriagtion control valse and or to prevent the flow of water back into the main water supply.

• Gate Valve: A manual on/off valve that uses a "gate" mechanism to drop a metal plate into place when the wheel handle is turned. This should only be used for emergency shut off and not regular on/off usage.

• Ball Valve: A rotating ball opens and closes the valve. Water passes through a hole in the center of the ball. It and is a better choice for regular usage. In fact, hose end timers (for drip irrigation) use ball valves as the internal mechanism.

• Check Valve: Many Backflow Preventers are check valves.

• Quick Coupler Valve: Often made of brass, it is an underground valve that is under constant pressure and designed to provide a quick water connection.

 2. Irrigation Control Valve. Also called remote control valves, they operate at 24VAC and are wired to an irrigation controller.  With the exception of anti-siphon valves, they are usually placed underground in valve boxes. Backflow Preventers are installed prior to the irriagtion control vales to prevent back siphonage. 

 

• Globe Valve: Inlet water comes into the  from underneath and leaves the valve at a 90 degree angle

• Angle Valve: Inlet water comes in from one side of the valve and leave the valves on the opposite side (in a straight line)

• Anti-Siphon Valve: An electric valve with a built-in atmospheric vacuum breaker. They must be placed 12: above the highest point in the irrigation system in order for the valve to successfully prevent backflow of water into the household water supply.

• Hydraulic Valve: Uses water pressure (modified via small flexible tubes) to operate the valve.

• Master Valve: Electric valve used in irrigation systems to control main line water flow to a manifold (group of irrigation valves).

Valve Box

A rigid plastic container which covers and protects underground irrigation valves. It has an access lid for valve maintenance. See also Valve, Controller, Direct Bury Wire, Two Wire. 

Valve Zone

See Zone.

Velocity

The speed of water traveling through a pipe. For irrigation systems, water velocity should never exceed 5 feet per second. When water velocity is very high on a systme and valves are shut off quickly, water hammer may occur. See Water Hammer.

Velocity Head

The small amount of energy required to put water in an irrigation system into motion. It is a negligible amount and generally not considered when calculating Total Dynamic Head. See also Pressure Head, Total Dynamic Head, Elevation Head, Friction Head.

Voltage

Amount of electrical potential required to force one amp of current flow in a circuit against one ohm of resistance.

Volume

The volume of water flowing through irrigation pipe.  It is often expressed as a flow rate [e.g. gallons per minute (gpm), gallons per hour (gph) cubic feet per second (ft3/s), cubic meters per hour (m3/h), liters per minute (l/m), or liters per second (l/s)]. To calculate  the volume of water flowing through your system,  see Flow Rate.

 

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Water Hammer

When the velocity of water flowing in a pipe is very high and is subsequently stopped, water hammer may occur, creating an an audible thumping sound in the pipes. It is generally caused by a rapid cessation of flow (e.g. a valve is closed quickly). High-velocity water has a lot of kinetic energy (KE). When the water is stopped rapidly, the KE is converted to potential energy.

Velocity is increased as pipe wall thickness increases or the pipe is reduced in size.. Therefore, water hammer is more common in schedule 40 PVC pipe than the thinner-walled Class 200. Thinner walls are more flexible and will also absorb more kinetic energy than a rigid, thick-walled pipe. If the pipe has been sized too small (thus creating the higher velocity), a shock wave may be created when the valve shuts off quickly. See also Kinetic Energy, Water Hammer Arrester.

 

Water Hammer Arrester

A mechanical device usually installed to an existing water system where water hammer is present. With a properly designed system, water hammer should not be present, thus eliminating the need for a water hammer arrester. See also Water Hammer.

Water Meter

A device used to measure the flow of water. See also Flow Rate.

Water Pressure

See Pressure.

Water Source

See Point of Connection.

Water Table

Upper level of the sub-surface water zone (goundwater).

Water Window

The amount of time in a day that is available to water a given area. For example, a shrub-planted area in a business park may have few restrictions regarding available watering times and, hence, has a large water window within which to irrigate the shrub area.  On the other hand, a school playing field may be fully occupied during school hours with school kids. After school, and into the evening, it is active with soccer games. Since that field can only be watered when no one is using it, the water window for the playing field is small.

Watering Zone

See Zone.

Weather Sensor

See Rain Sensor, Soil Moisture Sensor, Controller,

Well

A hole in the ground to access sub-surface water. A pump is often used to bring well water to the surface for irrigation.

Winterization

The process of removing water from irrigation pipes fittings, sprinklers, and drip emitters to protect them from freezing water in winter. As water turns into ice and expands, it can crack pipe and fittings and damage other irrigation components.

Wire

Irrigation systmes using electic valves and contollers will use low-voltage direct-bury wire or two-wire systems to power the valves. See also Direct-Bury Wire, Two-Wire, Controller, Valve.

Wire Gauge

A method/standard for denoting wire size. The larger the gauge number, the smaller the wire.

Working Pressure

See Dynamic Water Pressure.

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Xeriscaping

A landscape design technique that utilizes drought tolerant and native plants to create a finished product that requires no regular irrigation.

 

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Y Ball Valve

A 2-outlet ball valve that allows for connection of garen hose and drip system from the same hose bibb, faucet, spigot, or hydrant.

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Zone

Also called a watering zone, a "zone" is an individual watering area controlled by a single irrigation valve. It may be a group of sprinklers or a drip irrigation system. When designing an irrigation system, plan individual zones so that each contains plants with similar watering requirements. Watering zones should also consider micro climate factors like amount of sun exposure vs. shade, and design elements like sidewalks and driveways. With proper planning, you can create zones that allow flexible programming on your irrigation controller. See also Valve, Controller.