CSLB Trade — Plumbing (C-36) — All Questions
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60 questions
A water heater must be installed so that:
- a.the burner faces a combustible wall
- b.it is fully enclosed with no access
- c.the controls are hidden behind drywall
- d.it is accessible for inspection, service, and replacement✓
Water heaters must be located and installed with adequate access and clearances for inspection, servicing, and replacement. Enclosing the appliance without access violates the code and manufacturer listing. Required working space keeps the unit serviceable and safe.2022 California Plumbing Code (CPC) §507.0
The temperature-sensing element of a water heater T&P relief valve must be located so that it senses:
- a.the incoming cold water
- b.the water in the top 6 inches of the tank✓
- c.the flue gas temperature
- d.the room air temperature
The T&P valve's temperature element must extend into the top 6 inches of the tank, where the water is hottest, so it responds to dangerous overheating. Sensing cooler water lower in the tank would delay relief. Correct placement is essential to the valve's protective function.2022 California Plumbing Code (CPC) §608.3
A thermal expansion tank installed on a water heater system must be:
- a.supported so its weight is not carried by the connecting piping✓
- b.installed only on the hot outlet
- c.left unpressurized
- d.filled completely with water
An expansion tank, especially when full of water, is heavy and must be independently supported so its weight does not stress or break the piping. The air side is precharged to match system pressure. Proper support and precharge let the tank absorb thermal expansion reliably.
Water hammer arrestors are installed on a water distribution system primarily to:
- a.absorb the shock of quick-closing valves and reduce pipe noise and damage✓
- b.raise system pressure
- c.prevent backflow
- d.filter sediment
Quick-closing valves, such as those on clothes washers and dishwashers, cause a pressure surge (water hammer) that bangs pipes and can loosen joints. Water hammer arrestors provide a cushion of air or a piston to absorb that shock. They are installed near the quick-closing valve they protect.2022 California Plumbing Code (CPC) §609.10
An outdoor hose bibb (sillcock) must be protected against backflow by:
- a.a check valve on the water heater
- b.a pressure-reducing valve
- c.an expansion tank
- d.an atmospheric or listed hose-connection vacuum breaker✓
A hose bibb can create a cross-connection when a hose is submerged in contaminated water, so it must have a hose-connection vacuum breaker (or be a listed anti-siphon type). This device admits air to break any back-siphonage. It protects the potable supply from garden or utility contaminants.2022 California Plumbing Code (CPC) §603.5.7
Each fixture supply to a lavatory or water closet is commonly fitted with an angle stop primarily to:
- a.arrest water hammer
- b.allow the fixture to be shut off individually for service✓
- c.reduce the flow rate
- d.prevent backflow
An angle stop (fixture shutoff valve) lets a single fixture be isolated for repair or replacement without shutting off water to the whole building. It is installed on the supply riser to the fixture. This is a convenience and service requirement, not a backflow or flow-control device.
A water heater installed in an attic must be reached by a passageway and working platform. A typical minimum requirement is a solid, continuous passageway not less than:
- a.6 inches wide
- b.12 inches wide
- c.48 inches wide with stairs
- d.30 inches wide with a level working platform at the appliance✓
Attic-installed water heaters generally require a solid passageway at least 30 inches wide from the access opening to the appliance, plus a level working platform in front of the service side. A light and receptacle are also commonly required. These provisions let the unit be serviced safely.
Cross-connection control in a potable water system is intended to:
- a.increase water pressure at fixtures
- b.reduce pipe corrosion
- c.prevent nonpotable or contaminated water from entering the potable supply✓
- d.silence water hammer
Cross-connection control uses air gaps and backflow prevention devices to keep contaminated or nonpotable water from flowing back into the drinking water system. Backflow can occur by back-siphonage or back-pressure. Protecting every actual or potential cross-connection is a core plumbing safety requirement.2022 California Plumbing Code (CPC) §603.2
A floor drain located in a room that is used infrequently may lose its trap seal by evaporation. The approved way to keep the seal is to provide:
- a.a trap primer or an approved trap seal protection device✓
- b.a larger trap arm
- c.a second floor drain nearby
- d.a deeper cleanout
In little-used areas, water in a floor drain trap can evaporate and let sewer gas enter. A trap primer periodically adds water to maintain the seal, or an approved barrier-type trap seal device may be used. This keeps the required 2-to-4-inch seal intact.
A plumber replaces a water heater in a finished basement over a slab where a leak would not damage anything below, but the local code still requires spill protection. If a drain pan is installed, its drain must:
- a.be capped until a leak occurs
- b.connect directly into the sanitary sewer without an air gap
- c.discharge by gravity to an approved location where it will be readily observed✓
- d.loop upward before discharging
When a drain pan is installed, its drain line must run by gravity to an approved discharge point where a leak becomes readily visible, so the problem is noticed early. It must not tie directly into the sanitary drainage system without proper separation. Visibility of the discharge is the key requirement.2022 California Plumbing Code (CPC) §507.5