Free CIT Exam Flashcards

A fixed spray applies roughly 1.5 to 2.0 in/hr while a gear-driven rotor applies roughly 0.4 to 0.6 in/hr. On one zone the spray area floods long before the rotor area is watered. What must match within a zone is precipitation rate, not brand or body style.

A nozzle series whose flow is scaled to arc, so a quarter-circle nozzle discharges about one quarter the GPM of a full-circle nozzle at the same radius. Every arc on the zone then applies the same inches per hour. Non-MPR nozzles leave the quarter heads badly over-watered.

PR (in/hr) = 96.3 x total GPM / area (sq ft). The constant 96.3 converts gallons per minute spread over square feet into inches per hour. Use the total flow of the zone and the total area that zone actually covers.

Heads are spaced so each one throws water all the way to the next head, which is about 50 percent of the diameter of throw. Sprinklers apply the most water close to the head, so the overlap is what creates uniform coverage. Tighten spacing further on windy sites.

When the zone's precipitation rate is higher than the soil's intake (infiltration) rate, which shows up as runoff or puddling. Split the required run time into several short cycles with soak periods between them. The total water applied does not change, only the delivery.

An articulated riser assembly (typically three street ells, or flexible pipe) between the lateral and the head. It absorbs mower and vehicle impact, lets you set head height to finished grade, and keeps that shock from snapping the lateral fitting off the pipe.

Class pipe is rated by pressure: Class 200 means 200 psi working pressure at 73 F in every diameter. Schedule pipe is rated by wall thickness, so its pressure rating falls as diameter grows - a 4 in Schedule 40 is rated far lower than a 1/2 in Schedule 40.

Primer softens and cleans both the pipe end and the socket so the cement can chemically fuse them into one piece; it is not just a cleaner. Prime, cement, seat with a quarter turn, hold, and do not pressurize until the cement maker's cure time for that size and temperature has passed.

With barbed insert fittings clamped with stainless-steel clamps, or with compression fittings. Solvent cement does not bond polyethylene at all. PE stays flexible in cold soil, which is why it is common for laterals in hard-freeze regions.

Suction-side pressure drops below the water's vapor pressure, so bubbles form and then collapse violently in the impeller. It sounds like gravel in the pump and it pits the impeller. Fix the suction side - clogged screen, undersized or leaking suction line, too much lift - not the discharge side.

Backsiphonage is backflow caused by negative pressure in the supply, such as a water main break or heavy hydrant use pulling a vacuum. Backpressure is backflow caused by downstream pressure exceeding supply pressure, from a pump, elevation, or thermal expansion. Vacuum breakers stop only the first.

Backsiphonage protection only. It installs downstream of the control valve, at least 6 in above the highest downstream outlet, and it may not stay under continuous pressure (12 hours or less at a time). No shutoff valve may be installed downstream. Some local codes require more height.

A PVB is a testable assembly that may stay under continuous pressure, so one unit upstream of all the zone valves protects the whole system. Set it at least 12 in above the highest downstream outlet. Like the AVB it stops backsiphonage only, never backpressure.

Two independently loaded check valves in series with test cocks. It protects against both backsiphonage and backpressure, but it is approved for low-hazard (pollutant) connections only. Where local code permits, a DCVA may be installed below grade in a vault.

Two check valves plus a relief valve that dumps to atmosphere the moment the zone between the checks loses its pressure differential. It is the only assembly accepted for high-hazard (contaminant) irrigation connections, such as systems with chemical injection. It installs above grade, commonly at least 12 in, and the relief port must never be submerged.

Call 811 (or the local one-call center) and wait the required notice period for the utilities to mark the site. Marks expire and must be re-requested if the work is delayed. Hand-dig inside the tolerance zone around every marked line.

Industry practice caps blowout at about 80 psi on rigid PVC and about 50 psi on flexible polyethylene, and never above the lowest-rated component on that zone. Volume (CFM) is what pushes the water out; raising pressure instead of CFM blows nozzles off and splits fittings.

High-velocity, heat-carrying air destroys the internal rubber checks and seats of a PVB, RP, or DCVA. Never blow compressed air through a backflow assembly. Drain it separately through its test cocks and leave the test cocks open for the winter.

The system is full of air. Charging it fast drives that air ahead of the water as a surge that can blow nozzles out and crack fittings. Open the isolation valve part way, let each zone run to purge air and flush debris, then check heads and pressure.

Shut every fixture and zone, then watch the meter's low-flow indicator - the small triangle, star, or dial. Any movement means water is still passing, most often a control valve leaking by or a cracked lateral. This confirms a leak exists before you start digging for it.

Reclaimed or non-potable water. The color coding is required so nobody cross-connects that line to drinking water or a hose bib. Reclaimed sites also carry warning signage, and their quick couplers are typically keyed differently from potable ones.

A record drawing of what was actually installed - mainline routing, valve, splice, and sleeve locations, head layout - which almost always differs from the design plan. It is the fastest way to find a buried valve and the cheapest way to avoid cutting a mainline on the next repair.

V = I x R, or volts = amps x ohms. At a fixed 24 VAC the resistance decides the current: a shorted coil (low ohms) pulls too much current and faults the station output, while an open coil (infinite ohms) pulls none and the valve never opens.

Irrigation controllers send 24 volts alternating current to the zone solenoids, stepped down by a transformer at the controller. Because it is AC, the two solenoid leads have no polarity - either one may go to the common.

Roughly 20 to 60 ohms measured across the two solenoid leads with the meter on ohms; Rain Bird's own troubleshooting guidance uses this window for landscape valves. Confirm it against the specific manufacturer's spec, because coil ratings differ by model.

A broken coil winding, a cut field wire, or a corroded splice. Re-test at the valve with the solenoid leads disconnected: if the solenoid alone reads normal, the break is out in the field wiring, not in the valve.

Failed coil insulation, a nicked wire jacket touching the common, or two solenoids wired onto one station. A short pulls excess current and typically blows the controller fuse or trips a station fault. Isolate at the valve to tell the coil from the wire.

A resistance measurement injects the meter's own small current. Live 24 VAC on the circuit produces a false reading and can damage the meter. Voltage is tested live; resistance and continuity are tested dead and isolated.

Each solenoid gets its own station wire back to a numbered controller terminal, and all of the solenoids share one common return to the COM terminal, conventionally white. A broken station wire kills one zone; a broken common kills every zone past the break.

Wire nuts are not rated for wet or direct-burial use. Water wicks in, corrodes the copper, and raises circuit resistance until the valve stops pulling in. Use a listed waterproof direct-burial connector (grease-cap or gel-filled) and leave an expansion loop of wire in the box.

Voltage drop. Resistance rises with wire length and falls as the wire gets thicker, so long runs need a larger conductor - a smaller AWG number, 14 instead of 18. Too much drop leaves the solenoid under-volted, so it chatters or never lifts.

It steps 120 VAC line power down to about 24 VAC for the solenoids. Read the primary input and the secondary output with the meter on VAC. Line voltage present but no 24 VAC out means the transformer has failed, not the field wiring.

Start time(s), station run times, and watering days or interval. The program begins once per start time and then steps through its stations in order - it does not run only one station per start time.

Three start times are entered in the same program, and each start time re-runs the entire program from station one. Delete the extra start times. Shortening or lengthening run times will never fix a repeat-cycle problem.

Both use the same controller output, energized whenever any station runs. A master valve is a normally closed valve that leaves the mainline unpressurized between cycles; a pump start relay uses that 24 VAC signal to switch the pump's line-voltage circuit. Never wire a pump straight to the MV terminal.

With a wire tracker: a transmitter puts a tone on the station wire and a receiver follows the signal above ground to the solenoid. The same tool finds breaks, because the tone stops at the fault. Narrow the search first with the box lids and the mainline route.

It opens the circuit - wired into the controller's sensor terminals or in series with the common - so no solenoid can be energized even though the program keeps running its clock. That is why a controller can display a zone as running while nothing waters.

Static is measured with no water moving; dynamic is measured with the zone running. The gap between them is everything the water lost getting there - friction in pipe, fittings, valve, and meter, plus elevation. Sizing decisions use dynamic pressure at the head, never static at the point of connection.

1 psi = 2.31 ft of water, and 1 ft of water = 0.433 psi. Both come from the weight of water, so a 1 ft column exerts 0.433 psi at its base no matter how wide the pipe is. Diameter changes volume, not static pressure.

About 8.7 psi, from 20 ft x 0.433 psi/ft, before any friction loss is counted. Running the same 20 ft downhill adds that pressure instead. Elevation is separate from friction and is added to or subtracted from the pressure budget on its own.

Charts give loss in psi (or feet) per 100 ft for one pipe size, material, and flow rate, so multiply by the run length in hundreds of feet. Loss climbs steeply with flow and drops steeply as pipe size increases - one size up usually beats buying more pressure.

Faster water carries enough momentum that a quick-closing valve converts it into a pressure surge - water hammer - that fractures fittings and pipe. Low velocity also keeps friction loss reasonable. Size the pipe to the flow rather than forcing more GPM through a small line.

The shock wave from stopping moving water abruptly: a fast-closing solenoid valve, a quickly shut ball valve, or trapped air slamming shut. Reduce it by holding velocity down, upsizing pipe, using the valve's flow control to slow closure, and purging air at startup.

Both use the same diaphragm mechanism. A globe valve's inlet and outlet are in line, so it drops into a straight run of pipe. An angle valve turns the flow 90 degrees, which suits a bottom-inlet installation and generally costs slightly less pressure.

An angle control valve with an atmospheric vacuum breaker built into the same body, so each zone carries its own backflow protection. It must be above ground and at least 6 in above the highest head it serves (some codes require 12 in), and nothing that can create backpressure may be installed downstream of it.

It limits how far the diaphragm can lift, throttling the zone. Use it to trim excess pressure at the heads when they mist, and to slow the valve's closure. It is not a shutoff, and closing it too far can stop the valve from opening at all.

Opening it vents the diaphragm chamber and forces the valve open hydraulically with no electricity involved. If the zone runs on bleed but not from the controller, the fault is electrical - solenoid, field wire, or controller. If it will not run on bleed either, the fault is mechanical.

A filter and a pressure regulator. Emitter passages are small enough to plug on particles a sprinkler would pass straight through, and drip runs at far lower pressure than a sprinkler zone, so unregulated mainline pressure blows fittings off the tubing.

Openings per linear inch of screen, so a higher number is a finer screen that catches smaller particles. Landscape drip typically calls for roughly 120 to 200 mesh, about 75 to 125 microns. Always meet the emitter manufacturer's stated minimum.

It compares measured flow against the learned flow for the running zone. High flow means a broken mainline, a blown lateral, or a missing head; low flow means a stuck valve or a plugged zone. On an alarm the controller closes the master valve, which is why the pair is used on large or unattended sites.