CSLB C-36 Plumbing ContractorPlanning and EstimatingMedium
A plumbing contractor is installing a new solar hot water system for a residential property. The system includes evacuated tube collectors on the roof, a storage tank, and a pump. To protect the system from excessive pressure buildup due to thermal expansion and to prevent damage to components, which safety device is essential to install on the hot water storage tank and/or the solar loop?
- AA temperature and pressure (T&P) relief valve
- BA pressure-reducing valve (PRV)
- CA backflow preventer
- DA vacuum breaker
Show answer & explanationAnswer & explanation
Correct answer: A. A temperature and pressure (T&P) relief valve
A temperature and pressure (T&P) relief valve is a critical safety device for hot water storage tanks and solar thermal systems. It automatically opens to release water and/or steam if either the temperature or pressure exceeds safe limits, preventing tank rupture or system damage.
Why the other options are wrong
- B. A pressure-reducing valve (PRV) lowers incoming water pressure, but does not relieve excessive pressure caused by thermal expansion within a closed system.
- C. A backflow preventer stops contaminated water from flowing back into the potable water supply, unrelated to thermal expansion.
- D. A vacuum breaker prevents siphoning and protects against vacuum conditions, not overpressure or overtemperature.
Temperature and Pressure (T&P) Relief Valve
A safety device installed on water heaters, hot water storage tanks, and solar thermal systems that automatically opens to discharge water or steam when the temperature or pressure inside the tank exceeds a predetermined safe limit.
- Protects against dangerous overpressure and overtemperature conditions.
- Required by plumbing codes on all water heaters and hot water storage tanks.
- Must be installed with a discharge pipe leading to a safe discharge point.
- Regular testing is crucial to ensure proper operation.
Memory trick: High T, high P, T&P valve sets you free.