New Mexico CID MS-6 Lawn Sprinklers Examination

On an irrigation flow specification, what does GPM measure?

• AGallons per minute
• BGauge pressure in millibars
• CGround-pressure modulus
• DGrains of hardness per minute

Static water pressure on a potable lawn-sprinkler service is the pressure measured when:

• AThe system is pressurized and no water is flowing
• BOnly the farthest head is operating
• CThe service is drained and open to atmosphere
• DEvery zone is running at design flow

How much pressure does each foot of vertical water column add or subtract in an irrigation system?

• A1.0 psi per foot
• B2.31 psi per foot
• C0.433 psi per foot
• D0.043 psi per foot

A backflow assembly sits 10 ft above the water meter. How much static pressure is lost to elevation between the meter and the assembly?

• A0.43 psi
• B2.31 psi
• C4.33 psi
• D10 psi

Dynamic (working) pressure is the pressure measured when:

• AWater is flowing at the rate being designed or tested
• BThe compressor is blowing the system out for winter
• CThe meter is removed and the curb stop is closed
• DAll valves are closed and the line is locked up

A lateral climbs 12 ft from the zone valve to the highest head. What happens to pressure at that head from elevation alone?

• AIt decreases about 5.2 psi
• BIt is unchanged because laterals are small
• CIt decreases 12 psi
• DIt increases about 5.2 psi

Water hammer on an irrigation mainline is most often produced by:

• ASudden stop of fast-moving water at a quick-closing valve
• BA pressure-reducing valve set too low
• CAn air-relief valve at a high point
• DSlow manual opening of a ball valve

Irrigation designers use the Hazen-Williams equation primarily to estimate:

• ASprinkler precipitation rate
• BSoil infiltration rate
• CFriction loss in pressurized pipe
• DReference evapotranspiration

What Hazen-Williams C-factor is customarily used for new smooth PVC irrigation pipe?

• A100
• B120
• C150
• D180

If pipe diameter and flow stay the same and the run is doubled, friction loss approximately:

• ADoubles
• BQuadruples
• CDrops by half
• DStays the same

A zone carries 20 GPM in 1-1/4 in. Schedule 40 PVC (inside diameter 1.380 in.). Using V = 0.4085 × GPM / d², what is the velocity?

• A4.3 ft/s
• B2.1 ft/s
• C7.4 ft/s
• D5.2 ft/s

A meter reads 72 psi static. The highest heads are 20 ft above the meter and no water is flowing. What static pressure is available at those heads?

• A80.7 psi
• B52 psi
• C63.3 psi
• D72 psi

In Hazen-Williams friction, loss varies with flow to about the 1.85 power. If flow in a given pipe is doubled, friction loss becomes about:

• A3.6 times as large
• BFour times as large
• CUnchanged
• DTwice as large

The first head needs 42 psi. It sits 18 ft above the meter, and friction from the meter to that head is 7 psi. What minimum static pressure is required at the meter?

• A49 psi
• B67 psi
• C27 psi
• D57 psi

Hydrozoning a lawn-sprinkler design means grouping stations so that:

• AThe largest possible GPM is placed on the first station
• BEvery valve on the site uses the same nozzle catalog number
• CAreas with similar water need, sun, soil, and slope share a valve
• DTurf, shrubs, and annuals are mixed on one valve to save wire

If a zone’s precipitation rate exceeds the soil’s infiltration rate for the run time used, the usual field result is:

• AA drop in nozzle pressure that self-corrects the rate
• BHigher distribution uniformity
• CRunoff, puddling, and wasted water
• DAn automatic increase in available GPM

In an arid, windy New Mexico climate, the preferred automatic start window for turf spray and rotor zones is:

• AWhenever the controller happens to finish the previous program
• BMidafternoon, when air temperature is highest
• CEarly morning, before wind and evaporative demand peak
• DLate evening only, so leaves stay wet all night

Cycle-and-soak programming is used when:

• AThe water meter is larger than 1 in.
• BThe controller has unused stations that must be filled
• CA single long run would exceed infiltration and cause runoff
• DMatched-precipitation nozzles are not available

When winterizing a potable lawn-sprinkler system with compressed air, the safest field practice is to:

• ALeave the backflow charged so the relief valve can dump air
• BPressurize the main with all zone valves closed, then open them
• COpen a zone before applying air and blow zones one at a time within the sprinkler manufac…
• DUse the highest compressor pressure available so the job finishes in one pass

Head-to-head coverage means sprinklers are spaced so that:

• AThe wetted radius just reaches the next head
• BHeads are 80 percent of the throw diameter apart
• COnly the corners of a lawn receive overlap
• DOne row of heads can water the entire site from one edge

The precipitation-rate formula used in U.S. customary irrigation design is:

• APR (in/hr) = 96.3 × GPM / area (sq ft)
• BPR (in/hr) = GPM × area (sq ft) / 96.3
• CPR (in/hr) = 96.3 × area (sq ft) / GPM
• DPR (in/hr) = 231 × GPM / spacing (ft)

A matched spray nozzle delivers 1.80 GPM on a 15 ft by 15 ft square spacing. What is the zone precipitation rate?

• A0.77 in/hr
• B1.16 in/hr
• C0.48 in/hr
• D1.80 in/hr

A turf zone must apply 0.50 in. Its precipitation rate is 1.50 in/hr. How long should the station run, ignoring uniformity adjustments?

• A20 minutes
• B45 minutes
• C180 minutes
• D33 minutes

A half-circle matched-precipitation nozzle discharges 2.0 GPM at the design pressure. What should the matching full-circle nozzle discharge?

• A1.0 GPM
• B2.0 GPM
• C4.0 GPM
• D8.0 GPM

Why are conventional spray heads and gear-drive rotors not placed on the same valve?

• ASpray heads cannot be spaced head-to-head
• BThey use different colors of control wire
• CTheir precipitation rates and operating pressures do not match
• DRotors cannot operate on potable water

A south-facing turf panel in full sun borders a north-facing turf strip in building shade. The correct design response is to:

• APut both panels on one valve and use the sunny run time
• BPut both panels on one valve and use the shady run time
• CSeparate the panels onto different hydrozones so run times can differ
• DRaise nozzle pressure on the shady panel only

On a steep lawn slope, the designer should prefer:

• AMixing rotors and sprays so the slope averages out
• BThe highest available spray precipitation rate to finish before runoff starts
• CLow precipitation-rate nozzles and cycle-and-soak scheduling
• DOne row of part-circle heads at the bottom only

Sustained wind across a spray or rotor zone should be handled in layout by:

• ADeleting head-to-head overlap so streams do not collide
• BIncreasing spacing toward 60 percent of the diameter
• CTightening spacing and, where possible, using lower-trajectory nozzles
• DRaising operating pressure to punch through the wind

A rotor discharges 3.0 GPM on an equilateral triangular spacing of 25 ft. What is the precipitation rate? Use area = 0.866 × S × S.

• A3.46 in/hr
• B0.46 in/hr
• C0.53 in/hr
• D0.93 in/hr

A matched spray zone has 4 quarter-circle nozzles at 0.80 GPM, 6 half-circle nozzles at 1.60 GPM, and 2 full-circle nozzles at 3.20 GPM. What is the zone flow?

• A12.8 GPM
• B16.0 GPM
• C19.2 GPM
• D24.0 GPM

Static pressure at the meter is 78 psi. The last head is 14 ft above the meter. Design-flow losses are 9.5 psi in pipe, 10 psi in the backflow, and 3.5 psi in the zone valve. What residual pressure remains at the last head?

• A78 psi
• B55 psi
• C49 psi
• D41 psi

A zone must put 0.50 in of water in the driest part of the pattern. Precipitation rate is 0.75 in/hr and lower-quarter distribution uniformity is 0.70. What run time should be programmed?

• A40 minutes
• B28 minutes
• C57 minutes
• D75 minutes

The constant 96.3 in the precipitation-rate formula exists because:

• APVC pipe has a Hazen-Williams C of 96.3
• BA standard spray head throws 96.3 in. at 30 psi
• CThere are 96.3 gallons in a cubic foot
• DOne gallon spread over one square foot is about 1.604 in. deep, and 1.604 × 60 minutes is…

When locating sprinklers on a plan, the first heads should be placed:

• AOnly next to the zone valve to shorten laterals
• BOn a random offset so patterns do not look mechanical
• CIn the exact center of each turf panel
• DAt corners and along edges, then filled inward to keep head-to-head spacing

How many minutes are required to apply 0.40 in. at a precipitation rate of 0.80 in/hr?

• A48 minutes
• B50 minutes
• C20 minutes
• D30 minutes

A rotor nozzle delivers 3.20 GPM on a rectangular 20 ft by 18 ft spacing. What is the precipitation rate?

• A0.86 in/hr
• B0.53 in/hr
• C1.71 in/hr
• D0.32 in/hr

A point of connection can supply 14 GPM at the design residual. Each planned spray head uses 1.75 GPM, and the lawn needs 16 heads for coverage. How should the designer circuit the valves?

• AFour heads per valve so the meter never sees more than 7 GPM
• BOne valve of 16 heads plus a booster on the 24 V station wire
• COne valve with all 16 heads, because coverage matters more than flow
• DTwo zones of 8 heads (14.0 GPM each), which use the full available 14 GPM

Spray nozzles on a zone are rated at 30 psi. After elevation, pipe, backflow, and valve losses, the last head has 22 psi. The most correct design response is to:

• AAccept the zone; any pressure above 15 psi is adequate for sprays
• BReduce pipe size to raise velocity and restore pressure
• CLower friction or zone GPM, or both, until the last head is near 30 psi
• DInstall unmatched larger nozzles at the far heads only

For a typical residential lawn-sprinkler mainline, the usual rigid pressure pipe is:

• ASchedule 40 or pressure-rated PVC
• BDWV foam-core drain pipe
• CUnreinforced garden hose
• DCorrugated single-wall drain tile

Compared with 1 in. Schedule 40 PVC, 1 in. Class 200 (SDR 21) PVC of the same nominal size has:

• AThe same inside diameter and the same friction
• BNo pressure rating and cannot be used on laterals
• CA thicker wall, smaller inside diameter, and more friction at the same GPM
• DA thinner wall, larger inside diameter, and less friction at the same GPM

A swing joint or flexible swing pipe is installed at a pop-up head mainly to:

• AReplace the need for a zone valve
• BConvert 24 V control power into water pressure
• CIncrease the nozzle precipitation rate
• DLet the head be set to grade and absorb wheel and mower loads without breaking the lateral

A solvent-welded PVC irrigation joint is made correctly when the installer:

• AUses PE insert clamps on PVC because they are faster
• BCements the joint under water so it will not leak later
• CPushes dry pipe into a dry fitting and relies on a friction fit
• DCuts square, deburrs, primers, cements, and seats the pipe with a quarter turn while the…

A valve box over a remote-control valve is installed so that:

• AThe lid sits at finish grade and the valve remains serviceable
• BThe box is buried 12 in. below grade to hide it
• CThe box replaces the need for waterproof wire connectors
• DThe box is airtight to keep the solenoid dry under pressure

PVC Class 200 pipe is pressure-rated 200 psi under the standard condition of approximately:

• A180°F continuous hot-water service
• BAny temperature, because class ratings never derate
• C32°F ice water only
• D73°F, with the allowable pressure falling as water temperature rises

Why is foam-core or solid-wall DWV PVC not acceptable as an irrigation pressure lateral?

• ASolvent cement will not stick to it under any condition
• BIt has a larger inside diameter than Class 200 of the same nominal size
• CIt is a different color than irrigation PVC
• DIt is not pressure-rated for continuous irrigation service and can burst

A Class 200 mainline run is 200 ft of pipe. Four 90° elbows are listed at 3 ft of equivalent length each and one tee is listed at 6 ft. The chart loss is 2.8 psi per 100 ft. What is the total friction loss?

• A7.0 psi
• B2.8 psi
• C5.6 psi
• D6.1 psi

A lateral carries 25 GPM. Velocity in 1 in. Schedule 40 (ID 1.049 in.) is about 9.3 ft/s. In 1 in. Class 200 (ID 1.189 in.) it is about 7.2 ft/s. What is the correct pipe decision if the design limit is 5 ft/s?

• AEither 1 in. pipe is acceptable because both are called 1 in.
• BUse 1 in. Class 200 only, because 7.2 ft/s is close enough
• CUpsize; both 1 in. walls exceed 5 ft/s at 25 GPM
• DDownsize to 3/4 in. to raise pressure