CSLB C-36 Plumbing ContractorRough-in PlumbingHard
A plumbing inspector notes that a relief valve discharge pipe from a water heater is terminated directly into a floor drain. What is the primary reason this installation violates the California Plumbing Code (CPC)?
- AThe discharge pipe must be insulated.
- BThe discharge pipe must terminate with an air gap.
- CThe discharge pipe must be larger than the relief valve outlet.
- DThe discharge pipe must be made of copper or galvanized steel.
Show answer & explanationAnswer & explanation
Correct answer: B. The discharge pipe must terminate with an air gap.
The California Plumbing Code (CPC) mandates that the discharge pipe from a temperature and pressure (T&P) relief valve must terminate with an air gap. This prevents potential back-siphonage of contaminated water from the drain into the potable water system through the relief valve, protecting the water supply from contamination.
Why the other options are wrong
- A. Insulation is not a code requirement for relief valve discharge pipes.
- C. While discharge pipes have minimum sizing requirements, this isn't the primary reason for a violation when terminating directly into a drain.
- D. The material of the discharge pipe is specified (e.g., CPVC, copper, galvanized steel, polypropylene), but direct termination without an air gap is the more critical violation.
T&P Relief Valve Discharge
The safe and visible termination of the pipe carrying hot water from a water heater's temperature and pressure relief valve, designed to prevent scalding and system overpressure.
- Prevents building of dangerous pressure/temperature.
- Must discharge to a safe, visible location.
- Requires an air gap to prevent cross-connection.
Memory trick: T&P pipe, don't be a dunce, air gap always, all at once.