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Irrigation Glossary



Valve   Device to control flow. Valves used in pressurized systems include:

  • alfalfa- Outlet valve attached to the top of a short vertical pipe (riser) with an opening equal in diameter to the inside diameter of the riser pipe and an adjustable lid or cover to control water flow.  A ring around the outside of the valve frame provides a seat and seal for a portable hydrant.  Typically used in border or basin irrigation.
  • angle- Valve configured with its outlet oriented 90 degrees from its inlet.
  • air vent (air relief, air release)- Device that releases air from a pipeline automatically without permitting loss of water.
  • air vacuum, air relief- Device that releases air from a pipeline automatically without permitting loss of water or admits air automatically if the internal pressure becomes less than atmospheric.
  • back flow prevention-  Check valve that allows flow in one direction.  ...  See specific valve for details.
  • ball-
    • Valve in a pipeline used to start or stop flow by rotating a sealed ball with a transverse hole approximately equal to the diameter of the pipeline.  Ball rotation is typically 90 degrees for a single-port control ... 
    • Valve with an internally mounted ball with a hole in the center for water to pass through. (Rotation of the ball one-fourth turn opens and closes the valve.)
  • butterfly-Valve in a pipeline to start or stop flow by rotating a disk 90 degrees.  The disk is about the same diameter as the pipeline. ...
  • check- Valve used in a pipeline which allows flow in only one direction.
  • chemigation- Valve especially designed to be used with the injection of chemicals in an irrigation system.
  • corporation stop- Quarter turn valve similar to a ball valve with two exceptions. Internally there is a circular disk rather than a ball, and there is no attached handle.
  • curb stop- Physically the same as corporation valve but used at a different location.
  • drain valve
    • automatic- Spring loaded valve that automatically opens and drains the line when the pressure drops to near zero.
    • flushing- Valve on the end of a line to flush out dirt and debris.  May be incorporated into an end plug or cap.
  • float valve- Valve, actuated by a float, that automatically controls the flow of water.
  • foot valve- Check valve used on the bottom of the suction pipe to retain the water in the pump when it is not in operation.
  •  flow control- Valve with automatically adjusts to provide a predetermined downstream flow.
  • gate- Valve in a pipeline used to start or stop water flow.  May be operated by hand with or with mechanical assistance or by high or low voltage (solenoid) electric controlled mechanical assistance.  Gate valves consist of seated slide or gates operated perpendicular to the flow of water.  Head loss through a gate valve is typically less than a globe valve, but more than a ball or butterfly valve.
  • globe- Valve in a pipeline used to start or stop water flow. Globe valves stop flow by positioning a disk and gasket over a machined seat about the same diameter as the pipe.  Globe valves are limited to smaller sizes because of the high velocities and very high head loss through the valve.
  • hydraulic- Irrigation zone valve which uses small flexible tubes and water under pressure to provide the actuation signal from the controller to the valve.
  • isolation- Any mechanical valve used to isolate a section of a piping system.
  • master- Valve used to protect the landscape from flooding in case of a ruptured main or malfunctioning downstream valve.  The master valve is installed on the mainline after the backflow preventer (in some systems). 
  • orchard- Outlet valve installed inside a short vertical pipe (riser) with an adjustable cover or lid for flow control.  Similar to an alfalfa valve, but with lower flow capacity.  Typically used in basin irrigation.
  • pilot- Small valve used to actuate a larger one.
  • pressure regulating- Valve designed to automatically provide a preset downstream pressure in a hydraulic system.
  • pressure relief- Spring loaded valve set to open at a pressure slightly above the operating pressure, used to relieve excessive pressure and surges.
  • pressure sustaining- Valve designed to provide a mini mum preset upstream pressure.
  • quick coupling- Permanently installed valve which allows direct access to the irrigation mainline. A quick coupling key is used to open the valve. 
  • remote control- Valve which is actuated by an automatic controller by electric or hydraulic means.  Synonymous with automatic control valve.
  • surge- Device in a pipe T fitting to provide flow in alternate directions at timed intervals.  Used in surge irrigation.
  • swing check- See check.
  • vacuum relief valve- Valve used to prevent a vacuum in pipelines and avoid collapsing of thin-wall pipe.

Valve-in-head sprinkler Sprinkler head having an integrally mounted valve.

Vapor pressure head  Pressure head at which the liquid (water) will vaporize or boil at a given temperature.

Velocity Is the speed at which water moves through the system (pipe).

Vertical turbine pump  Pump having one or more stages, each consisting of an impeller on a vertical shaft, surrounded by stationary and usually symmetrical guide vanes.  Combines the energy-imparting characteristics of axial-flow and propeller pumps.

Voids ratio Ratio of the volume of voids (pores) to the volume of soil.

Voltage Force required to push and pull a stream of electrons through a circuit.

Volute Refers to the flow path of water and its associated pump casing as it leaves the impeller of a pump.

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