Irrigation Terms and Definitions
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Glossary Index
- Automatic drains
- See Drains (automatic)
- AVB (Atmospheric Vacuum Breaker)
- The lowest grade of backflow prevention equipment. When the pressure drops, the AVB allows air to enter the line to prevent back siphonage of contaminated water into the water supply. AVBs do not protect against back pressure.
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- Backflow Preventer
- An absolutely critical piece of equipment which serves to prevent the flow of contaminated water from the lateral lines back into the public water supply. Backflow preventers include AVB (Atmospheric Vacuum Breaker), PVB (Pressure Vacuum Breaker), DCA (Double Check Assembly), and RPZ (Reduced Pressure Zone) devices.
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- Ball valve
- A type of valve in which a round ball rotates to turn the flow on and off. The ball has a hole through the center such that water flows when the hole is aligned parallel to the direction of flow.
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- Bleed valve
- A small screw, usually in the top of an automatic valve, used to turn the valve on manually. An external bleed will spill water outside of the valve (inside of the valve box) to activate the valve. An internal bleed will spill water internally (to the downstream side of the valve) so the valve box stays dry and water is not wasted.
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- Class pipe
- A technically incorrect but commonly used name used to refer to SDR pipe.
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- Controller
- A mechanical or electronic device which instructs the station valves to operate.
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- DCA (Double Check Assembly)
- A backflow preventer consisting of two shut off valves at either end, two spring loaded serviceable check valves, and four test ports to allow testing of the performance of the device.
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- Drains (automatic)
- Automatic drains are sometimes installed in lateral lines to allow the water to drain from the pipe between waterings. They are recommended in areas where the ground freezes, but not recommended in warm climates because drains can hide valve leaks.
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- Ell
- A fitting which has a 90 degree bend to route pipe around a corner, sometimes called an "elbow."
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- FIPT
- Fem ale Iron Pipe Thread. The larger of the two threaded parts, with threads on the inside of the hole.
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- Fitting
- A part used to connect two pipes, or another fitting and a pipe.
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- Flow Control
- A device that controls flow independent of pressure drop.
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- Freeze switch
- A switch that opens the common line and interrupts watering whenever the temperature falls below a certain value. Watering is enabled as soon as the temperature rises above the setpoint.
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- Gate Valve
- A type of valve where flow is stopped by a sliding plate that is controlled by a turning handle. The handle typically turns a dozen or so times to close the valve.
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- Globe Valve
- A type valve where a washer presses on a round opening to shut off the water flow. The handle turns several revolutions from full open to full closed. The sink and outdoor faucets in most homes are globe valves except for single lever and push/pull faucets.
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- Gear Driven Rotor
- A type of rotor sprinkler where the rotating motion is achieved by a water driven gear mechanism.
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- Glue
- A solvent based adhesive used to permanently attach a pipe to a fitting or valve, or to attach two fittings together.
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- GPM
- Gallons per Minute, a flow rate. Multiply GPM by 3.9 to obtain the flow rate in liters per minute.
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- Hose Bib
- This is just another name for a faucet outside of your house.
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- Impact sprinkler
- A type of rotor sprinkler where the rotating motion is provided by a moving arm which strikes the water jet leaving the nozzle.
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- Interval program
- A watering schedule which operates at a regular frequency which is defined by the number of days between watering events. An interval program might water every 10 days or every 15 days instead of every Wednesday.
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- Kinetic energy
- The energy stored in moving water. When moving water stops suddenly, this kinetic energy is converted to potential energy and a brief pressure spike results.
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- Lateral lines
- This is a term used to describe the pipes downstream from each station valve. Any particular lateral line will not be under pressure unless that particular station is being watered.
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- Main line
- The pipe which carries water to the station valves.
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- Master valve
- A electric valve which opens whenever any station is watering, and closes when no station valves are on, shutting off the pressure in the main line. A master valve will greatly reduce any water loss due to a leaky station valve because the leaky station valve can only leak while the master valve is providing pressure to the system. Also, if you damage the irrigation main line, a master valve will control water loss so the main can be repaired without shutting off the water supply. A master electric valve is typically the same type of valve as you would use for your station valves, but rather than being installed downstream from your main line and connected to a station output in your controller it is installed upstream at the front of the main line and connected to the "master" or "pump" connection in your controller. Not all controllers support a mater valve or pump- be sure to check the features before buying a controller.
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- MIPT
- m ale Iron Pipe Thread. The part of the joint with the threads on the outside.
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- Moisture sensor
- A sensor, usually installed in the ground, which disables watering when the soil is wetter than the setpoint for the sensor.
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- Multiple start times
- A controller feature that allows a program to pe operated multiple times on the same watering day. This is important to allow the water time to soak in on steep slopes of clay soils.
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- nip ple
- This word should have two p's and no space in it, but we spell it this way so visitors to our site won't trigger their surf protection software for dirty words. These are a short piece of pipe threaded on both ends, typically used to connect a sprinkler to a fitting. Nip ples are typically only an inch or two long, but can be as long as a two or three feet when used for shrub sprinklers. This sounds like a funny name for this part, but the dictionary defines a nip ple to be "an appurtenance from which a fluid emanates" so you can see the function of this part does lead to its traditional name.
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- Nozzle
- The part of a sprinkler that defines the spray pattern.
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- PCD
- Pressure Control Device- a Toro sprinkler feature which controls pressure at the head to reduce misting.
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- Pop-up
- A sprinkler that rises from it's case when pressure is applied to the sprinkler, and retracts when the pressure is shut off.
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- Potential energy
- The energy stored while water is under pressure and not moving.
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- Precipitation rate
- The depth of water distributed on the ground over a given period of time. A typical precipitation rate for pop-up spray sprinklers is two inches per hour, about equal to a hard rain.
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- Primer
- Used to soften the surface of plastic pipe before applying glue.
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- Professional Grade parts
- Parts made especially for irrigation industry professionals. These are the parts that irrigation companies install, and they are higher quality and more reliable than the parts typically sold through large retail hardware warehouses. Click on this link to learn about our construction analysis of professional grade parts.
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- Program
- A predefined list of stations which operate sequentially each time the program is scheduled. The best controllers have three or more programs which can be operated on different schedules.
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- PRS
- Pressure Reducing Spray- A Rain Bird sprinkler feature which controls pressure at the head to reduce misting and protects against extreme water loss in the event a nozzle falls off of the sprinkler stem.
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- PRV
- Pressure Reducing Valve- a pressure regulator installed between the water meter and the backflow preventer. The purpose of the PRV is to reduce the pressure to the sprinkler system when excess pressure is present. If excess pressure is dropped through friction losses (by using smaller diameter pipe) water hammer will result.
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- Pump start
- A controller feature which turns on a pump or master valve whenever a station is watering.
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- PVB (Pressure Vacuum Breaker)
- A type of backflow preventer which is similar to the AVB, but which has a strong spring to help force the device to open to atmosphere when the pressure drops.
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- PVC
- Poly Vinyl Chloride, a type of plastic used for irrigation pipe and fittings.
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- Radius
- The distance from the middle to the edge of a circle. For a sprinkler, this is the distance from the sprinkler to the edge of the spray pattern.
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- Rain delay
- A controller setting that allows watering to be interrupted for a period of time. If the delay is programmable, you can set it to delay watering for a specific period of days and the controller will resume watering automatically after the delay period.
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- Rain switch
- A switch that opens the common line and interrupts watering as long as the rain switch is moist after a rain. Watering is automatically enabled several days after a rain. Some rain switches have an adjustable disable period.
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- RPZ (Reduced Pressure Zone)
- Similar to the DCA, except with the device designed to open to atmosphere when the forward pressure drop falls below a preset value.
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- Riser
- A fixture, usually used in shrub areas, on which a nozzle is attached. Risers do not move up and down at the beginning and end of the watering cycle.
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- Rotor sprinkler
- A type of sprinkler where a stream of water is moved back and forth across the area being watered. While the watering is not uniform at any one instant, it is uniform over a period of several minutes or longer.
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- SAM
- Seal-a-Matic- A Rain Bird sprinkler feature (essentially a check valve) which prevents the loss of water from low heads after watering is stopped.
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- Schedule 40
- A standard for pipe sizes that is rated for higher operating pressure than most SDR pipe at smaller diameters. As the pipe diameter of schedule 40 pipe increases, the maximum operating pressure rating drops steadily, unlike for SDR pipe.
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- SDR pipe
- A standard for pipe size where the SDR (standard dimension ratio) is the diameter of the pipe divided by the wall thickness. All diameters of a given SDR number have the same maximum operating pressure rating, so for very large diameters, SRD pipe often has a higher pressure rating than schedule 40 pipe! The "40" in schedule 40 does not represent the ratio of pipe diameter to wall thickness for schedule 40 pipe. At smaller diameters, schedule 40 pipe has a thicker wall than SDR 21 pipe.
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- Seasonal adjust
- A control which adjusts all station times by a set percentage.
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- Shut-off Valve
- A valve, usually a ball valve or gate valve, used to shut off the supply to a sprinkler system. The shut-off valve is located near the connection to the main water supply.
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- Slip
- A fitted joint that is secured by applying primer and glue, then slipping the two pieces together until the glue sets.
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- Solvent weld
- A joint that is secured by glue or solvent based cement. The same type of joint described under slip above.
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- Spray sprinkler
- A type of sprinkler where water is thrown evenly across the watered area at all times. The spray pattern is fixed and does not move during watering.
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- Start time
- The time that a particular program waters on its assigned day.
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- Station
- A portion of the sprinkler system with several sprinklers activated by one output from the controller. While usually only one valve is connected to each output, it is possible for two or more valves to be connected to one station if the controller transformer can handle the load.
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- Station time
- The length of time that a particular station waters when instructed.
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- Station valve
- The valve that supplies water to one station, or portion of the irrigation system.
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- Surge protection
- A controller feature where electrical power line fluctuations are isolated to prevent harm to the controller and provide for reliable retention of the program.
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- Swing joint
- An assembly of three ells and a nip ple to provide for convenient height adjustment of a sprinkler, and to reduce the chance of damage when a sprinkler is run over by a vehicle.
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- Teflon® tape
- A non-adhesive plastic tape used to seal threaded joints to prevent leakage.
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- Valve box
- A plastic enclosure which surrounds an underground valve to protect it yet still allow access to the valve.
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- Water day
- The day on which a particular program is assigned to execute.
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- Water hammer
- The sudden spike in water pressure observed when moving water is stopped suddenly. This occurs when the kinetic energy in the moving water is converted into potential energy. Pressure spikes due to water hammer are larger when schedule 40 pipe is used as opposed to SDR ("class") pipe. This is primarily because the inside diameter of SDR pipe of a given nominal size is larger than the inside diameter of schedule 40 pipe, resulting in a lower water velocity, and therefore less kinetic energy. A secondary reason is that SDR pipe is more elastic than schedule 40 pipe (since it has a thinner wall thickness in the common sizes) and absorbs the kinetic energy, reducing the maximum pressure during the water hammer spike.
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- Watering interval
- The number of days between watering events.
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- Wind switch
- A switch that opens the common line and interrupts watering whenever the wind speed exceeds a certain value. Watering is enabled as soon as the wind speed drops.
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