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 soil that drains very quickly, warms fast, and holds little water is MOST likely which texture?

• a.Sandy soil✓
• b.Silt
• c.Peat
• d.Clay

Sandy soils have large particles with large pore spaces, so water drains through rapidly and little is retained. They warm quickly in spring but dry out fast and need more frequent irrigation. Adding organic matter improves their water and nutrient holding capacity.

Most landscape and turf plants grow best in soil with a pH in which range?

• a.About 3.0 to 4.0 (strongly acidic)
• b.About 9.0 to 10.0 (strongly alkaline)
• c.Exactly 8.5 in all landscape soils
• d.About 6.0 to 7.0 (slightly acidic)✓

A slightly acidic to neutral pH of roughly 6.0 to 7.0 keeps most nutrients available for uptake by common landscape plants and turf. Extremely acidic or alkaline soils lock up nutrients even when they are present. Acid-loving plants like azaleas prefer the lower end of this range.

To lower the pH of an alkaline soil, which amendment is commonly used?

• a.Agricultural lime
• b.Elemental sulfur✓
• c.Gypsum for pH change
• d.Wood ash

Elemental sulfur is oxidized by soil bacteria into sulfuric acid, gradually lowering soil pH over weeks to months. Lime and wood ash raise pH, and gypsum changes soil structure and adds calcium without significantly changing pH. Sulfur is the standard choice to acidify alkaline soils.

In a fertilizer labeled 16-6-8, the three numbers represent the percentage of which nutrients in order?

• a.Phosphorus, nitrogen, potassium
• b.Potassium, phosphorus, nitrogen
• c.Nitrogen, phosphorus, potassium✓
• d.Nitrogen, potassium, phosphorus

The three-number N-P-K label always lists nitrogen first, phosphorus (as P2O5) second, and potassium (as K2O) third. So 16-6-8 is 16 percent nitrogen, 6 percent phosphorus, and 8 percent potassium by weight. Nitrogen drives leafy green growth, phosphorus supports roots and flowers, and potassium aids overall vigor.

A 50-pound bag of 20-0-10 fertilizer contains how many pounds of actual nitrogen?

• a.1 pound
• b.20 pounds
• c.5 pounds
• d.10 pounds✓

Actual nitrogen equals the bag weight times the nitrogen percentage, so 50 pounds times 0.20 equals 10 pounds of nitrogen. Landscapers use this calculation to apply the correct pounds of nitrogen per 1,000 square feet. Knowing actual nutrient content prevents over- or under-application.

Applying a 3-inch layer of organic mulch around plants primarily provides what benefits?

• a.It increases soil compaction around the roots
• b.It eliminates all irrigation needs
• c.It conserves moisture and suppresses weeds✓
• d.It raises soil pH sharply within days

A layer of organic mulch reduces evaporation, keeps soil temperatures more stable, and blocks light that weed seeds need to germinate. As it decomposes it also adds organic matter to the soil. Mulch is one of the most cost-effective water-saving practices in landscaping.

When planting a container-grown shrub, the top of the root ball should be placed at what level relative to the surrounding soil?

• a.6 inches below grade
• b.Buried under 4 inches of soil over the crown
• c.At or slightly above the surrounding grade✓
• d.12 inches below grade

The top of the root ball should sit at or slightly above finished grade so the crown does not sit in water and settle too deeply. Planting too deep suffocates roots and can rot the crown or trunk. Slightly high planting allows for minor settling while keeping the crown dry.

Gypsum is added to certain clay soils primarily to accomplish what?

• a.It lowers the soil pH significantly
• b.It kills weed seeds already in the bed
• c.It displaces sodium and improves structure✓
• d.It adds a large amount of nitrogen

Gypsum, calcium sulfate, supplies calcium that replaces sodium in sodic clay soils, improving aggregation and water penetration. It changes soil structure and drainage without appreciably altering pH. It is not a fertilizer and does not add nitrogen.

A newly planted tree needs staking. What is the correct staking practice?

• a.Wrap wire tightly around the bark
• b.Allow movement and remove stakes in a year✓
• c.Tie the trunk rigidly for at least five years
• d.Drive one stake straight through the root ball

Stakes should support the tree while allowing slight trunk movement, which encourages a stronger trunk and root system. Ties should be loose and use a broad, soft material, and stakes are typically removed after about one growing season. Rigid staking and bare wire damage the tree and create a weak, dependent trunk.

Which practice BEST improves drainage in a heavy clay planting bed?

• a.Compact the soil before planting
• b.Line the bottom of the bed with plastic sheeting
• c.Add fine sand only in small amounts
• d.Incorporate organic matter such as compost and improve grading✓

Blending compost and other organic matter into clay improves aggregation, creating larger pore spaces that let water move through. Combined with grading that directs excess water away, this relieves waterlogging. A small amount of sand can actually make clay worse by forming a concrete-like mix, and plastic traps water.

Proper plant spacing at installation should be based on what?

• a.The size of the nursery container only
• b.Fitting as many plants as possible
• c.The mature size and spread of the plant✓
• d.The current size of the plant

Plants should be spaced according to their expected mature width so they fill in without overcrowding. Spacing based on current small size leads to crowding, poor air circulation, and disease as plants grow. Good spacing reduces long-term maintenance and pruning.

A soil amendment high in nitrogen but low in decomposition, like fresh wood chips tilled into soil, can cause what short-term problem?

• a.A large and rapid rise in soil pH
• b.Temporary nitrogen deficiency, or drawdown✓
• c.Excess nitrogen that burns the plants
• d.Immediate salt toxicity in the root zone

When high-carbon materials like fresh wood chips are mixed into soil, microbes decomposing them consume available nitrogen, temporarily starving plants of it. This nitrogen drawdown causes yellowing until decomposition slows. Using wood chips as surface mulch instead of tilling them in avoids the problem.

Cool-season turfgrasses such as tall fescue grow most actively in which conditions?

• a.Deep winter freezes only
• b.Cooler spring and fall temperatures✓
• c.Complete shade year round
• d.The hottest summer weeks

Cool-season grasses like tall fescue peak in growth during the cooler temperatures of spring and fall and slow down in summer heat. Warm-season grasses such as Bermuda are the opposite, thriving in summer. Choosing the right type for the climate reduces water and maintenance needs.

When establishing turf from seed, keeping the seedbed consistently moist is important because what?

• a.Water is needed only after sprouts appear
• b.Seeds germinate better when completely dry
• c.Germinating seeds and shallow roots die quickly✓
• d.Moisture prevents any weed growth at all

Germinating seeds and their tiny first roots sit near the surface and die rapidly if the seedbed dries out. Light, frequent watering keeps the top layer moist until seedlings establish deeper roots. Once established, watering shifts to deeper and less frequent cycles.

Rough grading followed by finish grading before planting is done primarily to accomplish what?

• a.To create low spots that hold water
• b.To increase soil compaction before planting
• c.To set surface drainage and a smooth planting bed✓
• d.To remove all topsoil from the site

Grading shapes the soil surface so water drains away from structures and toward intended outlets, and finish grading creates a smooth, even bed for planting or turf. Poor grading causes ponding, erosion, and drainage complaints. Positive slope away from buildings is a core goal.

Compost is added to soil primarily to do what?

• a.To improve structure and add organic matter✓
• b.To compact the soil around new plants
• c.To serve as the only nutrient source
• d.To raise pH to strongly alkaline levels

Compost improves soil structure, increases water and nutrient holding capacity, and feeds beneficial soil microorganisms. While it adds some nutrients, its main value is as an organic amendment that improves overall soil health. It benefits both sandy and clay soils.

Which plant selection strategy BEST supports water-efficient landscaping in California?

• a.Drought-tolerant plants grouped by water need✓
• b.Mixing high- and low-water plants on one valve
• c.Select plants at random from the nursery
• d.Plant only high-water tropical species

Selecting drought-tolerant, climate-appropriate plants and grouping them by similar water needs, called hydrozoning, lets each irrigation zone be scheduled efficiently. Mixing high- and low-water plants on one valve forces overwatering of the low-water plants. Hydrozoning is a core MWELO efficiency practice.

A soil test reports very low phosphorus. Which fertilizer analysis would BEST correct it?

• a.21-0-0
• b.46-0-0
• c.0-0-60
• d.0-45-0✓

The middle number of the N-P-K label is phosphorus, so 0-45-0 supplies a high level of phosphorus and nothing else. 21-0-0 and 46-0-0 supply only nitrogen, and 0-0-60 supplies only potassium. Matching the deficient nutrient to the fertilizer analysis avoids waste.

Balled-and-burlapped (B&B) trees should have synthetic burlap and wire baskets handled how at planting?

• a.Removed only after two full growing seasons
• b.Left fully intact around the entire root ball
• c.Never touched once the tree is set
• d.Loosened and folded down, synthetics removed✓

Natural burlap decomposes, but synthetic burlap and twine do not and can girdle roots, so they should be removed or at least peeled back from the top of the root ball. Wire baskets are cut and folded down after the tree is set. This lets roots grow outward into the surrounding soil.

Slow-release (controlled-release) fertilizers are advantageous because they do what?

• a.They release all their nutrients in one day
• b.They contain no nitrogen or potassium
• c.They feed gradually, cutting burn and leaching✓
• d.They only work below freezing temperatures

Controlled-release fertilizers meter nutrients out over weeks or months, lowering the risk of fertilizer burn and reducing nutrient leaching into groundwater. This gives steadier plant growth and fewer applications. They are especially useful for sandy soils where quick-release nutrients leach fast.

The planting hole for a balled tree should generally be dug how wide relative to the root ball?

• a.Ten times the width and twice as deep
• b.The same width but twice as deep as the ball
• c.Two to three times the width of the ball✓
• d.Half the width of the root ball

A hole two to three times as wide as the root ball loosens surrounding soil so new roots spread outward easily, while keeping depth equal to the ball prevents settling and deep planting. Digging deeper than the ball causes the tree to sink and the crown to sit too low. Wide and shallow is the standard rule.

Salt buildup in soil from irrigation water or fertilizer is BEST managed by what practice?

• a.Deep irrigation to leach salts downward✓
• b.Adding more fertilizer to the planting bed
• c.Compacting the soil surface very firmly
• d.Reducing all watering to zero for a month

Applying a deep, thorough irrigation, called leaching, dissolves accumulated salts and carries them downward below the root zone where they no longer harm plants. This requires soil with adequate drainage. Adding more fertilizer would worsen the salt problem.

Finished grade around a building should slope away from the foundation at approximately what minimum for the first several feet?

• a.Sloping the grade back toward the building
• b.About 5 percent, or 6 inches over 10 feet✓
• c.Flat, with no slope in any direction
• d.A 45-degree drop at the foundation

A common standard is to slope soil away from a foundation about 6 inches over the first 10 feet, roughly a 5 percent grade, to carry surface water away from the structure. Sloping toward the building or leaving it flat allows water to pond against the foundation. Positive drainage protects the structure from moisture damage.

A French drain is BEST described as what?

• a.A raised planter box built along the wall
• b.A surface concrete drainage channel or swale
• c.A type of segmental retaining wall
• d.A gravel-filled trench with perforated pipe✓

A French drain is a trench filled with gravel around a perforated pipe that intercepts subsurface and surface water and carries it to a discharge point. Water enters the pipe through the perforations and flows by gravity away from the problem area. It is used to relieve soggy soils and protect foundations.

Before placing concrete pavers on a driveway, a compacted aggregate base is installed mainly to do what?

• a.A stable, load-bearing, well-draining foundation✓
• b.The final wearing surface of the driveway
• c.A replacement for perimeter edge restraints
• d.Added color and texture at the paved surface

A compacted crushed-aggregate base spreads loads, resists settling, and drains water away from the pavers, forming the structural foundation of the pavement. Without proper base compaction, pavers rut and settle unevenly. A sand setting bed and edge restraints are added on top of this base.