CSLB Landscaping (C-27) Trade — All Questions

A rotor sprinkler head throwing water 30 feet is BEST described as which type of irrigation component?

• a.A micro-spray for shrub beds
• b.A gear-driven rotor for large turf areas✓
• c.A drip emitter for point-source watering
• d.A bubbler for tree wells

Gear-driven rotors rotate a single stream back and forth and are designed for large open turf areas because of their long throw radius, typically 25 to 50 feet. Drip emitters, micro-sprays, and bubblers all deliver water at much shorter ranges for beds, shrubs, or trees.

Precipitation rate for a sprinkler zone is calculated using which formula?

• a.PR = area / (96.3 x GPM)
• b.PR = (96.3 x GPM) / area✓
• c.PR = PSI x GPM / 96.3
• d.PR = GPM x 60 x area

Precipitation rate in inches per hour equals 96.3 times the total GPM applied divided by the area in square feet covered by the heads. The constant 96.3 converts gallons per minute over square feet into inches per hour. This tells the designer how fast water is being applied so it can be matched to soil intake.

A zone has four heads each using 3 GPM covering a total area of 400 square feet. What is the approximate precipitation rate?

• a.About 2.9 inches per hour✓
• b.About 12 inches per hour
• c.About 0.03 inches per hour
• d.About 0.5 inches per hour

Total flow is 4 heads times 3 GPM equals 12 GPM. Using PR = 96.3 x 12 / 400, you get 1155.6 / 400, which is about 2.89 inches per hour. Rounding gives approximately 2.9 inches per hour.

Under California's MWELO (23 CCR §493.2.2), overhead irrigation is not permitted within what distance of any non-permeable surface?

• a.Within 12 inches
• b.Within 36 inches
• c.Within 18 inches
• d.Within 24 inches✓

Section 493.2.2(d)(10) provides that overhead irrigation shall not be permitted within 24 inches of any non-pervious surface. Drip or other low flow non-spray technology may be used inside that setback, and the setback may be planted or unplanted and surfaced with mulch, gravel, or other porous material. The requirement may be modified where no runoff occurs, where the adjacent hardscape drains entirely to landscaping, or where the designer demonstrates an alternative design preventing water waste. This is a setback from hardscape, not a limit on how narrow a planting area may be — the width rule is a separate provision at 10 feet.23 CCR §493.2.2(d)(10)

A reduced pressure principle (RP) backflow assembly is primarily used to protect a potable water supply against what?

• a.Both backsiphonage and backpressure hazards✓
• b.Freezing temperatures in the water supply line
• c.Excess flow velocity through the meter
• d.Low incoming water pressure only

An RP assembly is the highest level of mechanical backflow protection and guards against both backsiphonage and backpressure, making it suitable for high-hazard cross-connections. Irrigation systems using fertilizer or chemical injection are considered high hazard and typically require an RP device. It uses two check valves and a relief valve between them.

A pressure vacuum breaker (PVB) must be installed at what minimum height relative to the highest downstream sprinkler head or outlet?

• a.6 inches above the highest head
• b.12 inches above the highest head✓
• c.At the same level as the heads
• d.36 inches below grade

A pressure vacuum breaker must be installed at least 12 inches above the highest downstream outlet or sprinkler head so atmospheric venting works correctly against backsiphonage. It protects against backsiphonage only, not backpressure. Correct elevation is essential for the device to function.

An atmospheric vacuum breaker (AVB) has which key installation limitation?

• a.It protects against backpressure as well
• b.It requires two independent check valves
• c.It cannot be under continuous pressure✓
• d.It may be installed below the sprinkler heads

An atmospheric vacuum breaker protects only against backsiphonage and must be installed downstream of the last control valve with no shutoff valves after it. It cannot be under continuous pressure for more than about 12 hours and must sit above downstream outlets. It is the simplest and least expensive backflow device.

Water hammer in an irrigation system is BEST reduced by which measure?

• a.Removing all valves from the mainline
• b.Raising velocity above 10 feet per second
• c.Keeping velocity below about 5 feet per second✓
• d.Using undersized pipe on long runs

Water hammer is a pressure surge caused by fast-moving water stopping abruptly, often from quick-closing valves. Keeping design velocity at or below about 5 feet per second and using slow-closing solenoid valves reduces the surge. Oversized surges can burst pipe and fittings over time.

Which pipe material is MOST commonly used for buried irrigation mainlines under constant pressure in California?

• a.Galvanized steel with threaded joints
• b.Corrugated black flexible tubing
• c.Schedule 40 PVC rated for constant pressure✓
• d.Thin-wall aluminum tube and fittings

Buried pressure mainlines are commonly run in Schedule 40 PVC or an appropriate pressure-rated class of PVC because it handles constant pressure and resists corrosion. Lateral lines downstream of valves may use lighter class PVC since they are only pressurized during operation. Corrugated tubing is used for drainage, not pressurized supply.

As irrigation pipe diameter decreases while flow stays the same, what happens to friction (pressure) loss?

• a.Friction loss stays the same
• b.Friction loss becomes zero
• c.Friction loss decreases
• d.Friction loss increases✓

For a given flow rate, a smaller pipe forces water to move faster, and higher velocity dramatically increases friction loss along the pipe. This is why undersized pipe starves distant heads of pressure. Designers size pipe to keep velocity and friction loss within acceptable limits.

A drip emitter rated at 1 GPH means it delivers approximately how much water per hour?

• a.1 gallon per hour✓
• b.1 gallon per minute
• c.1 quart per day
• d.60 gallons per hour

GPH stands for gallons per hour, so a 1 GPH emitter releases one gallon over a full hour of operation. Drip systems are rated in gallons per hour because they apply water slowly and precisely at the root zone. This low, slow application reduces runoff and evaporation.

Distribution uniformity (DU) in an irrigation audit measures what?

• a.The total gallons of water used per month
• b.How evenly water is applied across the area✓
• c.The pressure rating of the pipe used
• d.The color and density of the turf

Distribution uniformity describes how evenly water is spread across a zone, comparing the driest areas to the average application. Higher DU means less water waste because you do not have to over-irrigate to compensate for dry spots. Poor uniformity commonly comes from mismatched heads, wrong spacing, or pressure problems.

Head-to-head spacing of spray heads means each head is spaced so its throw reaches what point?

• a.Only the center of the zone
• b.The base of the adjacent head✓
• c.Halfway to the next head
• d.Twice the distance to the next head

Head-to-head coverage, also called 100 percent overlap, spaces heads so each one throws water all the way to the adjacent head. Because spray heads apply less water at the outer edge of their radius, this overlap is required for even coverage. Spacing heads farther apart creates dry rings and poor uniformity.

A zone must deliver 18 GPM and the water meter supplies 12 GPM available flow. What is the BEST corrective action?

• a.Increase system pressure to 120 PSI
• b.Remove the backflow device
• c.Run all heads longer
• d.Split the zone into two smaller zones✓

When a zone's demand exceeds available flow, heads will not operate at their designed pressure and coverage suffers. Splitting the zone into two zones that each stay within the 12 GPM supply solves the problem. Raising pressure cannot create flow the meter cannot deliver, and removing the backflow device is unsafe and illegal.

A matched precipitation rate (MPR) nozzle set is designed to do what?

• a.Eliminate the need for a controller
• b.Increase the operating pressure at each head
• c.Reduce the number of valves needed
• d.Apply water at the same rate for any arc✓

Matched precipitation rate nozzles apply the same depth of water per hour whether the head covers a quarter, half, or full circle. Manufacturers scale each nozzle's flow to its arc so a quarter head uses about one-fourth the flow of a full head. This keeps the whole zone evenly watered on a single run time.

A smart irrigation controller that adjusts run times using local weather data is called what?

• a.An ET-based or weather-based controller✓
• b.A pressure-regulating master valve
• c.A manual mechanical dial timer
• d.An anti-siphon irrigation valve

An evapotranspiration (ET) or weather-based controller uses temperature, humidity, wind, and solar data to estimate plant water needs and adjust schedules automatically. This reduces overwatering compared with a fixed manual timer. MWELO encourages such controllers to improve landscape water efficiency.

A pressure-regulating device is added to a spray head when static pressure is too high. What is the typical target operating pressure for fixed spray heads?

• a.About 60 to 70 PSI
• b.About 100 PSI
• c.About 5 PSI
• d.About 30 PSI✓

Fixed spray heads are designed to operate near 30 PSI; much higher pressure causes misting and fogging that drifts away and wastes water. Pressure-regulating heads or in-line regulators bring high static pressure down to the efficient range. Rotors generally run at higher pressures than sprays.

Misting or fogging from spray heads is usually a sign of what condition?

• a.Broken lateral line
• b.Clogged emitters
• c.Pressure too high✓
• d.Pressure too low

When operating pressure is too high, the water leaves the nozzle atomized into a fine mist that drifts and evaporates instead of landing on the target area. The fix is to install pressure regulation so heads run at their rated pressure. Low pressure causes the opposite problem, poor throw and doughnut patterns.

An irrigation solenoid valve is operated by what signal from the controller?

• a.A low-voltage 24-volt AC signal✓
• b.A mechanical cable pull from the timer
• c.Line power at 240 volts AC
• d.A pneumatic air pressure signal

Standard automatic irrigation valves use a 24-volt AC solenoid that the controller energizes to open the valve. When the controller sends the low-voltage signal, the solenoid lifts a plunger and hydraulic pressure opens the diaphragm. This low voltage is safer and easier to run underground than line voltage.

Under MWELO, the Maximum Applied Water Allowance (MAWA) is based primarily on which factors?

• a.Only the total number of sprinkler heads
• b.Pipe diameter, valve count, and head spacing
• c.The brand of controller that is installed
• d.Reference ET, area, and adjustment factor✓

MAWA sets a water budget calculated from the local reference evapotranspiration (ETo), the landscape area, and an ET adjustment factor that reflects allowed plant water use. The designed landscape's estimated water use must stay within this allowance. This is the core water-budget concept of MWELO.CA MWELO (Title 23)

Subsurface drip irrigation is especially useful in which situation?

• a.Cooling a paved patio surface in the summer
• b.Filling a decorative garden pond
• c.Watering a steep concrete slope face
• d.Slopes and narrow strips prone to runoff✓

Subsurface drip places emitter tubing below the soil surface, delivering water directly to roots with virtually no overspray or runoff. This makes it well suited for slopes and narrow strips where spray irrigation would waste water on pavement. It also reduces evaporation and weed germination at the surface.

Cycling a station into several short run times instead of one long run is called cycle-and-soak and mainly prevents what?

• a.Freezing pipes in cold weather
• b.Clogged spray nozzles and inline filters
• c.Runoff on slow-draining soils and slopes✓
• d.Low water pressure at the heads

Cycle-and-soak breaks a long irrigation into shorter bursts with soak periods between, letting water infiltrate before more is applied. This prevents runoff when the precipitation rate exceeds the soil's intake rate, common on clay soils and slopes. It improves efficiency without changing total water applied.

A flow sensor connected to a smart controller is MOST useful for detecting what problem?

• a.A broken lateral line or stuck valve✓
• b.A sudden change in air temperature outdoors
• c.The color and density of the turf
• d.The pH level of the surrounding soil

A flow sensor measures real-time water flow and lets the controller compare it to expected values for each zone. Abnormally high flow signals a broken pipe or stuck-open valve, and the controller can shut the system down to prevent water loss. This protects against costly leaks and water waste.

To convert a flow of 12 GPM to gallons per hour for scheduling, what is the result?

• a.720 gallons per hour✓
• b.120 gallons per hour
• c.200 gallons per hour
• d.12 gallons per hour

There are 60 minutes in an hour, so 12 gallons per minute times 60 equals 720 gallons per hour. Converting GPM to GPH is useful when comparing zone flow to an hourly water budget. This simple multiplication helps estimate total water use.

A rain sensor or rain shutoff device connected to a controller does what?

• a.It increases run time during storms
• b.It measures the soil pH in the bed
• c.It boosts the water pressure at the heads
• d.It suspends irrigation after enough rainfall✓

A rain sensor interrupts the controller's watering cycle once it detects a set amount of rainfall, preventing irrigation during and shortly after storms. This avoids the waste of watering an already-wet landscape. Many California water agencies require or encourage rain shutoff devices on new systems.

A C-27 is designing an irrigation system that will inject liquid fertilizer into the mainline downstream of the potable point of connection. Which backflow assembly does that cross-connection call for?

• a.An atmospheric vacuum breaker on each control valve
• b.A pressure vacuum breaker set above the highest head
• c.A double check valve assembly at the point of connection
• d.A reduced pressure principle assembly at the connection✓

Injecting fertilizer makes the system a high-hazard (health hazard) cross-connection, and only the reduced pressure principle assembly is approved for high hazard under both backpressure and backsiphonage. The double check is rated for non-health hazards only. The pressure vacuum breaker and the atmospheric vacuum breaker both stop backsiphonage alone and neither is approved where chemicals are injected under pressure.

An atmospheric vacuum breaker is being considered for a small residential zone. Which installation condition rules it out on that zone?

• a.The zone runs for 45 minutes at a time
• b.The device would sit 14 inches above the highest head
• c.The zone uses spray heads rather than drip tubing
• d.A control valve is located downstream of the device✓

An atmospheric vacuum breaker has a float that must be able to open to atmosphere, so no valve may be placed downstream of it; a downstream valve holds the device under pressure and defeats it. A 45-minute run is well inside the 12-hour continuous pressure limit. Spray heads are a normal downstream use. Fourteen inches of elevation exceeds the six-inch minimum, so that placement is acceptable.

A pressure vacuum breaker is installed on a hillside system where a downstream booster pump was later added. Why is that combination a problem?

• a.The device requires a larger relief port for pump service
• b.The device must be relocated below the pump inlet
• c.The device cannot pass the flow a booster pump produces
• d.The device does not protect against backpressure✓

A pressure vacuum breaker guards only against backsiphonage. A downstream pump can push water back toward the supply as backpressure, which the device is not built to stop, so a reduced pressure principle assembly is needed instead. Flow capacity is a sizing matter, not the hazard. Placing the device below the pump would only make it worse. A pressure vacuum breaker has no relief port to enlarge.

On which irrigation system is a double check valve assembly an acceptable choice for backflow protection?

• a.A system fed in part from an on-site reclaimed water line
• b.A conventional turf system fed only from the potable main✓
• c.A system whose mainline passes through a sewage lift station vault
• d.A system with a chemical injection port on the mainline

The double check valve assembly is approved for continuous pressure but only where the hazard is non-health, which describes a plain turf system on potable water. Reclaimed water, chemical injection, and a mainline exposed inside a sewage vault are all health hazards, and each of those requires the reduced pressure principle assembly that vents to atmosphere when either check fouls.

An inspector rejects a reduced pressure principle assembly that was installed inside a below-grade valve box. What is the basis for the rejection?

• a.The assembly must be installed with the flow arrow pointing down
• b.The assembly must be within five feet of the water meter
• c.The relief port must discharge freely to atmosphere above grade✓
• d.The assembly must be protected from sunlight at all times

A reduced pressure assembly dumps water out of a relief port whenever the checks foul, so it has to sit above grade where that discharge is visible and cannot be submerged; a flooded box would let contaminated water enter through the port. There is no five-foot rule tying it to the meter. These assemblies are installed horizontally in the direction of the flow arrow, and sunlight is not the governing concern.

After a backflow assembly is installed on a new commercial landscape, what does the water purveyor normally require next?

• a.A dye test of the downstream laterals for cross-connections
• b.A pressure test of the mainline witnessed by the local building inspector
• c.A field test by a certified backflow tester before the system is used✓
• d.A letter from the designer stating the hazard level of the site

Backflow assemblies are mechanical devices that can pass a visual check and still leak, so purveyors require a field test by a certified tester at installation and on a recurring schedule after that. A mainline pressure test proves the pipe, not the assembly. A designer letter is not a substitute for a physical test. Dye testing laterals is not part of the acceptance of the assembly.

An anti-siphon control valve is being set on a bed that steps uphill from the valve manifold. Where must the valve be placed?

• a.At the lowest head in the zone so that the lateral is able to drain
• b.Above the highest head the valve serves, by the required clearance✓
• c.Level with the average elevation of the heads in the zone
• d.Inside a valve box with the bonnet at finish grade

An anti-siphon valve carries an atmospheric vacuum breaker in its bonnet, and that breaker only works when it sits above every outlet it protects, so the valve must be higher than the highest head in the zone. Setting it at the low point or at an average elevation leaves heads above the breaker. Burying it in a box defeats the device entirely, since the bonnet must be open to air.

A fire hydrant is flowed on the street and the irrigation system briefly draws water backward toward the main. What is this event called?

• a.Backpressure from the downstream zone
• b.Thermal expansion in the service line
• c.Backsiphonage caused by negative supply pressure✓
• d.Water hammer traveling back through the supply main

Heavy draw on the main drops supply pressure below the pressure in the irrigation piping, and the resulting vacuum pulls water backward, which is backsiphonage. Backpressure is the opposite case, where downstream pressure rises above the supply. Water hammer is a surge from a valve closing quickly. Thermal expansion raises pressure in a closed system and does not reverse flow direction.

A landscape sits 60 feet uphill of the water meter and the system feeds a booster pump at the bottom of the hill. Which backflow condition is created?

• a.Backsiphonage, because elevation lowers the available supply pressure
• b.Neither, because elevation gain cancels the pump pressure
• c.Neither, because the pump discharges away from the meter
• d.Backpressure, because the pump can exceed the supply pressure✓

A pump raises pressure on the downstream side, and any time downstream pressure can exceed supply pressure the system can push water back toward the main, which is backpressure. Backsiphonage requires a vacuum in the supply, which a pump does not create. A pump does not prevent reverse flow when it is off, and elevation gain does not cancel the pressure the pump can develop.

A homeowner asks a C-27 licensee to replace the corroded potable water service line from the city meter to the house while the crew is on site trenching for irrigation. How should the licensee respond?

• a.Decline or subcontract it, since a water service is plumbing work✓
• b.Perform the work, since the trench for it is already open
• c.Perform the work if the homeowner pulls the permit personally
• d.Perform the work if the pipe size matches the irrigation mainline

The C-27 classification covers landscape systems including irrigation and drainage, but the potable service supplying the building is plumbing and belongs to a plumbing classification, so it must be declined or subcontracted to a properly licensed contractor. An open trench, a matching pipe size, and who pulls the permit change nothing about which classification is authorized to do the work.16 CCR §832.27

A designer sizes a PVC mainline so that velocity stays at or below about five feet per second. What is the main reason for that limit?

• a.To hold friction loss under one psi per hundred feet
• b.To keep the pipe from collapsing when the system drains
• c.To keep the water temperature stable in the mainline
• d.To limit surge pressure when a valve closes quickly✓

Surge pressure from a closing valve rises with the velocity of the moving column, so capping velocity near five feet per second is how designers keep water hammer from splitting fittings. Pipe collapse on draining is not a pressurized-line concern. Friction loss is a separate calculation with no such fixed target. Water temperature in a buried line is not affected by design velocity.

A zone sits 30 feet higher than the point of connection. Roughly how much pressure is lost to elevation alone?

• a.About 10 psi
• b.About 13 psi✓
• c.About 3 psi
• d.About 7 psi

Every foot of elevation gain costs about 0.433 psi, so 30 feet costs roughly 13 psi, which must be subtracted before friction losses are even considered. The 3 psi figure would apply to about seven feet of rise, 7 psi to about sixteen feet, and 10 psi to about twenty-three feet. Underestimating this loss is the usual reason uphill zones run at poor pressure.

A drip zone is located 45 feet downhill from the valve. What does that elevation change do to pressure at the emitters?

• a.Has no effect, because drip emitters are self-adjusting
• b.Adds roughly 19 psi, which may require pressure regulation✓
• c.Has no effect, because the valve sets downstream pressure
• d.Removes roughly 19 psi, which may require a larger lateral

Falling elevation adds about 0.433 psi per foot, so 45 feet of drop adds roughly 19 psi, easily enough to blow emitters off tubing without a regulator. It is a gain, not a loss, so a larger lateral is not the fix. Only pressure-compensating emitters self-adjust, and only within a range. A control valve does not hold a fixed downstream pressure.

A gauge on a hose bibb reads 78 psi with nothing running and 52 psi while a rotor zone operates. What do these two readings represent?

• a.Design pressure and residual pressure at the head
• b.Service pressure and regulated pressure
• c.Static pressure and dynamic working pressure✓
• d.Surge pressure and operating pressure

Pressure with no flow is static pressure and pressure measured while water moves is dynamic or working pressure, and the difference is what friction and demand consume. Design pressure is a target the designer selects, not a gauge reading. Surge pressure is the spike from a closing valve. Regulated pressure is whatever a regulator is set to deliver.

A lateral carrying 15 GPM in one-inch pipe is losing too much pressure over a 300-foot run. Which change reduces friction loss the most?

• a.Increasing the lateral to the next larger pipe size✓
• b.Adding a second control valve on the same lateral
• c.Switching from solvent weld to gasketed fittings throughout
• d.Raising the controller run time for that station

Friction loss falls sharply as the inside diameter grows, so stepping up one pipe size is the direct fix for a long lateral. Fitting style changes losses only marginally. A second valve on the same lateral does not change the flow the pipe must carry. Run time affects how long water is applied and has no effect at all on pressure loss along the pipe.

Comparing Class 200 and Schedule 40 PVC of the same nominal size, which statement is accurate?

• a.Class 200 is rated for higher continuous pressure
• b.Schedule 40 has a larger bore and a lower pressure rating
• c.Class 200 has a thicker wall and a smaller bore
• d.Schedule 40 has a thicker wall and a smaller bore✓

Both share the same outside diameter, and Schedule 40 achieves its higher rating with a thicker wall, which leaves a smaller inside bore and slightly more friction loss. Class 200 is the thinner-walled, lower-rated pipe with the larger bore, so the first two statements reverse the relationship and the third assigns Class 200 traits to Schedule 40.

A crew is solvent-welding a PVC mainline joint on a warm day. Which step is required for a sound joint?

• a.Sand the spigot end smooth so the cement spreads evenly
• b.Chill the pipe end so the cement sets more slowly
• c.Wipe the socket with solvent thinner and let it dry fully
• d.Apply primer to soften both surfaces before the cement✓

Primer softens the PVC on both the pipe and the fitting so the cement can fuse them, and skipping it is the common cause of joints that weep under pressure. Thinner cleans but does not soften the surface. Chilling the pipe slows the chemical reaction rather than helping it. Sanding the spigot smooth removes material and can leave the joint loose.

Rotor heads on a turf zone keep snapping off at the riser when they are struck by mowers. Which detail should have been installed?

• a.A swing joint between the lateral and the head✓
• b.A brass nipple between the lateral and the head
• c.A cutoff riser set two inches below finish grade
• d.A check valve in the body of each rotor head

A swing joint lets the head move under impact and be reset to grade without breaking the lateral, which is why it is standard under rotors in turf. A brass nipple is rigid and transfers the impact straight into the fitting. A check valve stops low-head drainage but does nothing for impact. Setting a head below grade blocks the spray pattern.

Emitters on a new drip zone plug within the first season on a system fed from a well. What was most likely omitted at the head of the zone?

• a.An air and vacuum relief valve at the high point
• b.A pressure-compensating manifold on each run
• c.A flush cap at the end of each lateral
• d.A filter of roughly 150 to 200 mesh✓

Drip emitters have very small passages, so a fine filter in the 150 to 200 mesh range at the head of the zone is what keeps well sediment out of them. A compensating manifold addresses pressure, not particles. Air relief protects against soil being drawn in when the line drains. Flush caps help clear settled debris but do not stop it from arriving.

A drip zone is teed off a mainline that runs at 70 psi. What must be added for the emitters to operate correctly?

• a.A pressure regulator sized to the zone flow✓
• b.A larger valve to slow the entering velocity
• c.A second filter downstream of the emitters
• d.A booster pump sized to the emitter count

Most drip emitters are built for roughly 20 to 30 psi, so a regulator matched to the zone flow is what brings 70 psi down to the operating range and keeps fittings from blowing apart. A booster pump raises pressure that is already too high. A larger valve does not reduce downstream pressure. A filter placed after the emitters cannot protect them.

A single drip lateral runs from the bottom of a slope to the top of a 20-foot rise. Which emitter type keeps output even along that run?

• a.Pressure-compensating emitters rated over a pressure range✓
• b.Turbulent-flow emitters spaced at wider intervals up the run
• c.Vortex emitters installed only on the upper half
• d.Diaphragm emitters fed from a larger lateral

Pressure-compensating emitters hold a nearly constant discharge across a stated pressure band, which is exactly what a run that climbs 20 feet needs. Turbulent-flow emitters still put out more where pressure is higher regardless of spacing. Mixing emitter types on one lateral produces uneven output. A larger lateral reduces friction but does nothing about the elevation difference.

Inline drip tubing is being laid in a sandy bed and in a clay bed on the same property. How should emitter spacing differ?

• a.Identical, because emitter flow rate governs the wetted width
• b.Closer in the clay, because clay absorbs water more quickly
• c.Closer in the sand, because water moves down more than out✓
• d.Wider in the sand, because water travels farther laterally

Sand has large pores, so water drops nearly straight down and the wetted bulb is narrow, which calls for closer emitter spacing to join the bulbs. Clay spreads water laterally and tolerates wider spacing. Flow rate affects bulb size but does not remove the soil texture difference, and clay absorbs water more slowly rather than more quickly.

A subsurface drip zone under turf is drawing soil into the tubing each time the valve closes. Which component prevents this?

• a.A finer filter at the head of the zone
• b.An air and vacuum relief valve at the zone high point✓
• c.A pressure regulator set ten psi lower
• d.A flow sensor wired to the controller for that zone only

When the valve shuts, the draining lateral pulls a vacuum and sucks soil back through the emitters, and an air and vacuum relief valve at the high point breaks that vacuum by letting air in. A flow sensor only reports flow. Filtration protects against particles entering from the supply, not from the soil side. Lowering regulated pressure does not stop the drain-down vacuum.

After a zone shuts off, water keeps running out of the two lowest spray heads on a sloped lawn. What corrects this?

• a.Installing a master valve at the point of connection
• b.Raising the controller run time for that station
• c.Installing check valves in the low heads of the zone✓
• d.Adding a pressure regulator ahead of the zone valve

Water remaining in the lateral drains through whichever heads sit lowest, and check valves in those heads hold it back. Longer run times worsen the puddle. A master valve controls the mainline and has no effect on a lateral that is already full. Pressure regulation controls operating pressure and does not stop gravity drainage after shutoff.

Spray heads with a 15-foot radius are being laid out on a rectangular lawn. What spacing does head-to-head coverage call for?

• a.About 30 feet apart, at the full diameter of throw
• b.About 8 feet apart, at half the radius of throw
• c.About 15 feet apart, so each head throws to the next✓
• d.About 22 feet apart, at one and a half times the radius

Head-to-head layout means the stream from one head reaches the adjacent head, so spacing equals the radius, here about 15 feet. Spacing at 22 or 30 feet leaves the weak outer edge of each pattern unsupported and produces dry rings. Spacing at 8 feet doubles the water applied and wastes both heads and pressure.