Journeyman Plumber ExamWater Supply SystemsEasy
A plumber is installing a water service line from a municipal main to a new residential dwelling. The municipal water main pressure is consistently 80 PSI. The local plumbing code requires that the maximum static pressure within a domestic water distribution system not exceed 80 PSI. What device, if any, is required at the point of connection to the dwelling's water supply?
- ANo device is strictly required if the code allows 80 PSI as maximum.
- BA check valve.
- CA pressure reducing valve (PRV).
- DA backflow prevention assembly.
Show answer & explanationAnswer & explanation
Correct answer: A. No device is strictly required if the code allows 80 PSI as maximum.
If the municipal pressure is 80 PSI and the code allows a maximum of 80 PSI, then no pressure reducing valve (PRV) is strictly required to reduce the pressure. A PRV would only be needed if the municipal pressure exceeded the maximum allowable system pressure.
Why the other options are wrong
- B. A check valve prevents backflow but does not regulate pressure.
- C. A PRV is not needed as the municipal pressure (80 PSI) does not exceed the maximum allowed system pressure (80 PSI).
- D. A backflow prevention assembly is required based on cross-connection risk, not solely on pressure.
Water Pressure Regulation (PRV)
The control of water pressure within a plumbing system to maintain it within safe and acceptable limits, often achieved using a Pressure Reducing Valve (PRV).
- Plumbing codes typically set maximum allowable static pressure (e.g., 80 PSI).
- PRVs reduce high incoming pressure to a safer, more manageable level.
- Protects fixtures, appliances, and pipes from damage due to excessive pressure.
Memory trick: Pressure check: Is the supply too high for the code's eye?