CSLB C-36 Plumbing ContractorPlanning and EstimatingEasy
A plumbing contractor is installing a new water supply system in a residential property. The local water utility mandates the installation of a pressure-reducing valve (PRV) on the main water service line. What is the primary reason for installing a PRV in a residential plumbing system?
- ATo prevent water hammer in the piping.
- BTo protect fixtures and appliances from excessive water pressure.
- CTo filter sediment from the incoming municipal water supply.
- DTo increase the water pressure for upper-story fixtures.
Show answer & explanationAnswer & explanation
Correct answer: B. To protect fixtures and appliances from excessive water pressure.
A pressure-reducing valve (PRV) is installed when the incoming municipal water pressure is too high. Its primary function is to lower and regulate this pressure to a safer and more manageable level (typically 50-80 psi) to protect plumbing fixtures, appliances, and piping from damage.
Why the other options are wrong
- A. While a PRV can indirectly help reduce the severity of water hammer, its primary function is not water hammer arrestment.
- C. Water filtration is performed by dedicated filters, not PRVs.
- D. A PRV reduces pressure; it does not increase it. Pressure boosting is done by booster pumps.
Pressure-Reducing Valve (PRV)
A plumbing device installed on the main water supply line to automatically reduce and maintain incoming high water pressure to a safer, more consistent level within the building.
- Protects plumbing fixtures, appliances, and piping.
- Required when municipal pressure exceeds 80 psi (or local code).
- Typically set to maintain pressure between 50-80 psi.
Memory trick: PRV: Pressure Reduced, Valuables protected.