CSLB C-46 Solar ContractorElectrical and Plumbing CodesMedium
A solar contractor is installing a new solar thermal system that includes a potable water storage tank. According to the Uniform Plumbing Code (UPC) and California Plumbing Code (CPC), what is the primary purpose of requiring a temperature and pressure relief (T&P) valve on this tank?
- ATo ensure the water temperature remains within a comfortable range for bathing.
- BTo protect against dangerously high temperatures and pressures that could cause tank rupture.
- CTo allow for periodic drainage of the tank for cleaning and maintenance.
- DTo prevent excessive water pressure from damaging the tank and piping.
Show answer & explanationAnswer & explanation
Correct answer: B. To protect against dangerously high temperatures and pressures that could cause tank rupture.
The primary purpose of a T&P valve on a potable water storage tank in a solar thermal system, as mandated by UPC/CPC, is to protect against the catastrophic failure of the tank due to dangerously high temperatures and pressures. Overheating or over-pressurization can lead to tank rupture, which is extremely hazardous.
Why the other options are wrong
- A. Water comfort is a user preference, not the safety-driven purpose of a T&P valve.
- C. While drainage is possible, it's not the T&P valve's primary safety function.
- D. This is part of its function, but 'preventing damage' is secondary to preventing rupture from dangerous conditions.
T&P Valve Purpose
A safety device required on water heaters and storage tanks to relieve excessive temperature and pressure, preventing tank rupture and ensuring safety.
- Mandated by UPC/CPC.
- Protects against over-temperature and over-pressure.
- Prevents catastrophic tank failure/rupture.
Memory trick: T&P valve: too hot, too much pressure, it's the tank's last measure!