CSLB C-36 Plumbing ContractorPlanning and EstimatingEasy
A plumbing contractor is installing a new solar hot water system for a residential property. The system includes a storage tank that can reach high temperatures and pressures. Which safety device is absolutely essential to prevent dangerous over-temperature and over-pressure conditions in the storage tank?
- APressure-Reducing Valve (PRV)
- BWater Hammer Arrestor
- CTemperature and Pressure (T&P) Relief Valve
- DBackflow Preventer
Show answer & explanationAnswer & explanation
Correct answer: C. Temperature and Pressure (T&P) Relief Valve
A Temperature and Pressure (T&P) Relief Valve is a critical safety device designed to automatically open and discharge hot water if either the temperature or pressure in a water heater or storage tank exceeds a safe limit, preventing rupture or explosion.
Why the other options are wrong
- A. A PRV reduces incoming water pressure, but does not protect against over-temperature or over-pressure within the tank itself.
- B. A water hammer arrestor mitigates pressure surges from sudden valve closures, not continuous over-pressure or over-temperature.
- D. A backflow preventer stops contaminated water from entering the potable supply, unrelated to tank temperature/pressure.
Temperature and Pressure (T&P) Relief Valve
A safety device installed on water heaters and hot water storage tanks that automatically opens to discharge water if the temperature or pressure inside the tank exceeds predetermined safe limits, preventing catastrophic failure.
- Protects against both over-temperature and over-pressure.
- Required by plumbing codes for all hot water storage tanks.
- Must be properly sized and discharged to an approved location.
Memory trick: T&P valve: 'T' for 'Temperature', 'P' for 'Pressure' – always release to prevent disaster.