CIT flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

PSI to feet of head

One psi of static pressure supports a column of water 2.31 feet high; multiply psi by 2.31 to find equivalent head, or multiply feet of head by 0.433 to get psi.

Flow velocity limit in laterals

Design lateral pipe flow at or below 5 feet per second to limit friction loss, noise, and water hammer; mainlines are commonly limited to about 7 feet per second.

Precipitation rate formula

Precipitation rate in inches per hour equals 96.25 times the sprinkler's gallons per minute divided by the area it covers in square feet.

Total dynamic head

Total dynamic head is the sum of elevation lift, suction lift, friction losses through pipe and fittings, and the operating pressure required at the farthest head.

Nozzle flow versus pressure

Flow through a fixed orifice varies with the square root of pressure, so doubling the pressure increases flow by about 41 percent rather than doubling it.

Backsiphonage

Backflow caused by negative or sub-atmospheric pressure in the supply line, which pulls nonpotable water into the potable system, as can happen during a main break.

Backpressure backflow

Backflow that occurs when downstream pressure exceeds the supply pressure, such as from a boiler, booster pump, or elevated tank connected to the system.

RPZ assembly

A reduced pressure zone assembly has two independent check valves and a differential relief valve; it protects against both backpressure and backsiphonage at high hazard connections.

Air gap

A physical separation between the potable supply outlet and the flood-level rim of the receiving vessel; it provides the highest level of cross-connection protection.

Atmospheric vacuum breaker

An atmospheric vacuum breaker must be installed at least six inches above the highest downstream outlet, with no shutoff valves or continuous pressure allowed downstream.

Solenoid coil resistance

A healthy 24-volt irrigation solenoid coil typically measures about 20 to 60 ohms; infinite resistance indicates an open coil, and near-zero resistance indicates a short.

Controller transformer output

Irrigation controllers supply 24 volts AC to solenoid valves; measuring at the station terminal and common while a valve is active confirms the transformer and output are working.

Voltage drop rule

Keep voltage drop on valve wiring below about 10 percent of supply; long runs and undersized wire add resistance and can prevent valves from opening.

Rain sensor wiring

Most irrigation rain sensors are normally closed switches wired in series with the common wire; when rainfall is detected the circuit opens and irrigation stops.

Decoder system

A two-wire control architecture in which addressable decoders at each valve receive coded signals over a single path, replacing individual home-run wires to the controller.

Matched precipitation rate

Using sprinkler heads or nozzles with similar precipitation rates within one zone prevents overwatering and dry spots that occur when application rates differ.

Pressure-compensating emitter

A drip emitter that maintains a constant discharge, typically 0.5 to 2 gallons per hour, across a wide range of inlet pressures, keeping flow uniform along the zone.

Swing joint

A flexible fitting assembly of elbows and nipples that allows a sprinkler head to be adjusted for height, angle, and grade without stressing the lateral pipe.

Check valve in rotor

A device built into some rotors that holds water in the lateral when the zone shuts off, preventing low-head drainage and puddling at the lowest heads.

PVC solvent cementing

A joining method for PVC pipe using primer and solvent cement; apply primer, cement both surfaces, insert with a quarter turn, and allow proper cure before pressure testing.

Call 811 before digging

In the United States, call the free utility locate service before trenching; wait the required period and hand-dig near marked utilities to avoid damaging buried lines.

Mainline trench depth

Irrigation mainlines are typically buried 12 to 18 inches deep and below the frost line in cold climates, while laterals are commonly 6 to 12 inches deep.

Hydrostatic pressure test

New irrigation piping is tested at about 1.5 times design pressure, or at least 50 psi above working pressure, held for a specified period before backfilling.

Flushing before heads

Open and flush mainlines and lateral ends to remove debris before installing sprinkler heads and nozzles, since debris clogs nozzles, valves, and emitters.

Valve won't close

Common causes include debris trapped in the valve seat, a torn or worn diaphragm, or a solenoid plunger stuck in the open position, allowing flow to continue.

Winterization blowout

Remove water from irrigation lines with compressed air at moderate pressure, opening zones one at a time, to prevent freeze damage to pipe, valves, and backflow devices.

Low pressure diagnosis

Check for partially closed valves, clogged filters or screens, leaks, undersized pipe, or a failing pump before assuming that a sprinkler head is defective.

Water hammer causes

Sudden valve closure, high flow velocity, or missing air chambers and shock arrestors create pressure surges that can damage pipe, valves, and fittings.

Trench protective system

OSHA requires cave-in protection such as sloping, shoring, or trench boxes for excavations five feet deep or more, plus a means of exit within 25 feet.

GFCI protection outdoors

Outdoor and wet-location electrical circuits, including controller receptacles, require ground-fault circuit interrupter protection to reduce the risk of electric shock.

WaterSense labeled products

An EPA program identifying irrigation controllers and heads that meet water-efficiency criteria; many rebate programs and local codes require or reward these products.

Backflow tester certification

Most jurisdictions require annual testing of backflow prevention assemblies by a certified tester, with results reported to the local water authority.