CSLB Trade — Plumbing (C-36) — All Questions
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60 questions
During rough-in you must pressure test the water piping. Which is a typical acceptable test for the water distribution system before concealment?
- a.Run all fixtures at once for one minute
- b.No test is needed
- c.Fill and eyeball for leaks only
- d.A water or air pressure test held at the required pressure for the required time with no drop✓
The water distribution piping is proved with a water (or air) pressure test held at the required pressure for the required duration with no pressure drop, confirming there are no leaks before concealment. Skipping the test, merely eyeballing, or briefly running fixtures does not satisfy the required pressure test.2022 California Plumbing Code (CPC) §610.0
PEX tubing is being routed through a framing environment where it could be exposed to sunlight through a skylight for extended periods. What limitation applies?
- a.PEX has a limited UV exposure rating and must be protected from prolonged sunlight per the manufacturer listing✓
- b.PEX must be painted black
- c.PEX may be left in direct sun indefinitely
- d.PEX has no exposure limits
PEX has a limited ultraviolet (UV) exposure rating and must be protected from prolonged sunlight in accordance with its listing, or it can degrade. Claiming no limits, indefinite sun exposure, or that painting it black solves the issue all conflict with the UV limitation.2022 California Plumbing Code (CPC) §604.1
Where must a readily accessible full-open shutoff valve be provided on the building water supply?
- a.Only at the farthest fixture
- b.Nowhere; a curb stop at the street is sufficient
- c.Only at the water heater
- d.On the water supply pipe to the building, so the entire supply can be shut off✓
A readily accessible full-open control valve is required on the building supply so the whole building can be isolated for repairs. A valve only at the water heater or only at the farthest fixture does not isolate the building, and relying solely on the street curb stop does not meet the on-premises shutoff requirement.2022 California Plumbing Code (CPC) §606.2
To allow individual maintenance, where does good practice and code generally require shutoff (angle stop) valves in a dwelling?
- a.Nowhere inside the dwelling
- b.Only at the water heater
- c.Only at the meter
- d.At each fixture supply (for example under lavatories and at water closets)✓
Fixture shutoff (angle stop) valves at each fixture supply let a single fixture be isolated for repair without shutting down the whole house. Valves only at the meter or heater, or none at all, would force a full shutoff for any minor fixture repair.2022 California Plumbing Code (CPC) §606.5
A two-story home has the main run in the crawlspace and risers to the second floor. To minimize pressure loss to upstairs fixtures during simultaneous use, which strategy is best?
- a.Size the trunk and risers for the combined demand and keep developed length and fittings reasonable✓
- b.Remove the shutoff valves
- c.Undersize the risers to save material
- d.Add extra elbows to slow the water
Sizing the trunk and risers for the combined simultaneous demand while keeping developed length and fittings reasonable minimizes friction and pressure loss to upstairs fixtures. Undersizing risers, adding elbows, or removing valves would increase loss or reduce control, not help.2022 California Plumbing Code (CPC) §610.0
A dental office has vacuum and treatment equipment connected to the potable supply, presenting a health hazard with possible backpressure. Which premise-isolation assembly is appropriate?
- a.Reduced pressure principle assembly (RP)✓
- b.Hose bibb vacuum breaker
- c.Double check valve
- d.Atmospheric vacuum breaker
A health hazard with possible backpressure requires a reduced pressure principle assembly (RP) for premise isolation. An AVB and hose bibb vacuum breaker protect only against back-siphonage, and a double check is limited to low hazards, so none of those suffice for a health hazard with backpressure.2022 California Plumbing Code (CPC) §603.0
After installing a new RP assembly on a high-hazard connection, what ongoing requirement typically applies?
- a.It only needs testing if it leaks visibly
- b.It self-certifies and never needs testing
- c.No further action ever
- d.Periodic testing by a certified tester (commonly annually) to verify it still functions✓
Testable backflow assemblies such as RP devices require periodic testing by a certified tester, commonly on an annual basis, to verify continued protection. They do not self-certify, are not exempt from testing, and testing is not limited to only when visible leaks occur.2022 California Plumbing Code (CPC) §603.0
Threaded steel (galvanized) water pipe is run horizontally. What is the typical maximum horizontal support spacing?
- a.12 feet✓
- b.6 feet
- c.32 inches
- d.3 feet
Threaded steel pipe is rigid and heavy, so the support table typically allows a maximum horizontal spacing of about 12 feet. 6 feet applies to small copper, 3 feet to small CPVC, and 32 inches to PEX, all of which are shorter than steel's allowance.2022 California Plumbing Code (CPC) Table 313.3
A single check valve is proposed as backflow protection for a high-hazard chemical connection. Why is this not acceptable?
- a.A single check cannot be installed horizontally
- b.A single check is not a tested, fail-safe assembly and provides inadequate protection for a health hazard✓
- c.A single check is too expensive
- d.A single check increases flow too much
A single check valve is not a tested, redundant, fail-safe assembly, so it does not provide the reliability required for a health (high) hazard, which needs an RP or air gap. Cost, flow increase, and orientation are not the reasons a single check is disallowed for high hazards.2022 California Plumbing Code (CPC) §603.0
A homeowner reports faucets that hammer and leak, and you measure 105 psi static. Besides installing arrestors at quick-closing valves, what is the primary corrective action?
- a.Remove all aerators
- b.Increase pressure to 120 psi
- c.Install a pressure-reducing valve to bring static pressure to 80 psi or less✓
- d.Do nothing under 110 psi
Since 105 psi exceeds the 80 psi limit, the primary correction is a pressure-reducing valve to lower static pressure to 80 psi or less, which also reduces stress and hammer. Increasing pressure worsens the problem, removing aerators does not fix pressure, and doing nothing violates the 80 psi limit.2022 California Plumbing Code (CPC) §608.2