Hunter Industries - The Irrigation Innovators

Glossary of Irrigation Terminology (Index Q-Z)

Here is a glossary of commonly used terms in the irrigation industry:

A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z

R

RADIUS OF THROW – The distance from the sprinkler head to the furthest point of water application.

RECLAIMED WATER – Water that has been collected after an original use for reuse.

REMOTE CONTROL – Device that can be used to activate electronic irrigation valves from a given distance away from the irrigation controller.

RESISTANCE – In electrical systems, it is the resistance to the flow of current. It can be compared to friction loss in an irrigation piping system. Resistance causes a drop in voltage along the length of a wire and is measured in ohms.

ROTORS – Gear-driven sprinklers that spray a solid stream of water and rotate slowly in a circular pattern.

RUN-OFF – Water that is not absorbed by the soil and turf to which it is applied. Run-off occurs when water is applied at too great a rate, or for too long a time.
S

SCHEDULING – The procedure of establishing and implementing the time and amount of irrigation water to apply.

SCHEDULING COEFFICIENT (SC) – The SC is a measure of uniformity of water distribution in any specific irrigated area as it relates to the precipitation rate of the entire area. Stated another way, the SC is an indication of the additional sprinkler run time necessary to compensate for dry areas. In a catchment test, the average precipitation rate for all catchments is divided by the one lowest precipitation rate to establish the SC of the system. (A perfect SC of 1.0 states that all catchments in a zone fill to the same level.)

SPRAY HEADS – Sprinklers that emit a fan-type spray of small droplets of water. These heads generally have a radius of 19' and shorter.

SPRINKLER DISTRIBUTION PATTERN – Two-dimensional water depth-distance relationship measured from a single (or multiple) sprinkler head(s).

STATIC PRESSURE – The measurement of water pressure when the water is at rest in a closed system.

STATION – A circuit on an irrigation controller that can be programmed with a run time separate from other circuits and provides power to one or more remote control valves.

SWING JOINT – A combination of threaded pipe and fittings used between the pipe and sprinkler that allows movement to be taken up in the threads rather than as a sheer force on the pipe. Can also be used to raise or lower sprinklers to final grade without plumbing changes.
T

TIMER – See “controller.”

TRAJECTORY – The trajectory of a sprinkler is the measurement (in degrees) of the angle of the water projecting out from the sprinkler’s nozzle. A trajectory of 0° would indicate a flat projection of water out from the nozzle.
U

UNIFORMITY – The evenness of precipitation over a given area.

UNION – A pipe fitting used to connect two lengths of pipe in such a way that neither has to be rotated.
V

VALVE – A device to control flow. Valves used in pressurized systems include:

  • Angle – A valve configured with its outlet oriented 90 degrees from its inlet.
  • Automatic Control Valves (also called remote control valves) – These valves are used in conjunction with automatic timers and are a convenient and economical way of delivering water to lawns, plants, and gardens. Inline automatic control valves are usually installed underground in valve boxes, and anti-siphon automatic control valves are installed 6" to 12" above the highest sprinkler in the zone. Anti-siphon valves are a type of backflow preventer and are not approved in all areas.
  • Ball – A valve with a single arm or lever that requires a quarter turn to turn on or off. This single action is convenient, but caution should be used and the valve should not be turned on or off too quickly, as damage could result. Ball valves have resilient seats and are a better choice than gate valves if they are to be frequently used.
  • Drain Valve, Automatic – Spring loaded valve that will automatically open and drain the line when the pressure drops to near zero.
  • Gate Valves – Valves that have a wheel type handle. Several turns of the handle are required to turn off a gate valve. Gate valves are most commonly used on mainline pipes with high water pressure or high water flow. Because several turns are required, they are easier to turn off and the potential for damage caused by water hammer is reduced. Gate valves have a brass to brass seat and are not recommended for frequent use.
  • Globe – A valve configured with its outlet oriented 180 degrees from its inlet but having flow path with directional changes and a gasketed disk moving perpendicular to the flow path to open or close the valve.
  • Hydraulic – An irrigation zone valve which uses small flexible tubes and water under pressure to provide the actuation signal from the controller to the valve. Requires special freeze protection in northern climates.
  • Isolation – Any mechanical valve used to isolate a section of a piping system.
  • Manual Control Valves – These valves are not as common as they once were. The manually controlled sprinkler system eliminates having to move a hose-end sprinkler around from spot to spot, but the user does not have the convenience of the automatic system. Usually manual control valves incorporate an anti-siphon type backflow preventer.
  • Pressure Regulating – A valve designed to automatically provide a preset downstream pressure in a hydraulic system.
  • Quick Coupling – A permanently installed valve which allows direct access to the irrigation mainline for use of hoses. A quick coupling key is used to open the valve.
  • Remote Control – A valve which is actuated by an automatic controller by electric or hydraulic means.

VELOCITY – The speed at which water travels through a pipe. The designer should use caution when designing a system where the water velocity exceeds 5 feet per second (see “water hammer”).

VOLUME – Expressed in 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). Volume is used to describe either the amount of water available or the amount of water used.

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

WATER HAMMER – The surging of pressure which occurs when a control valve is suddenly closed. In extreme conditions, this surging will cause the pipes to vibrate or create a pounding noise. Water hammer is most commonly caused by fast closing valves and/or high velocity water flow.

WATER METER – A device used to measure the flow of water.

WATER WINDOW – The amount of time in a day that is available for irrigation to occur at a site.

WIRE – In an automatic sprinkler system, low voltage direct burial wire is used to connect the automatic control valves to the controller. The most frequently used wire for commercial applications is single strand, heavy gauge direct burial copper wire. (The larger the gauge number, the thinner the wire.) The most frequently used wire for the home sprinkler system is multi-strand. Color-coded, multi-strand sprinkler wire has several coated wires together in one protective jacket.
Z

ZONE – A zone is the area to be watered by one sprinkler valve.