Journeyman Plumber ExamWater Supply SystemsEasy
A plumber is performing a final pressure test on a newly installed water distribution system inside a commercial building. The system is designed for a maximum working pressure of 80 PSI. According to commonly adopted plumbing codes, what is the minimum test pressure the system should be subjected to for at least 30 minutes, without any leakage?
- A120 PSI
- B80 PSI
- C150 PSI
- D100 PSI
Show answer & explanationAnswer & explanation
Correct answer: A. 120 PSI
Most plumbing codes (e.g., UPC, IPC) require water distribution systems to be tested at a minimum pressure of 125 PSI or 1.5 times the working pressure, whichever is greater, for at least 15-30 minutes. Since 1.5 times 80 PSI is 120 PSI, and this is greater than the 125 PSI minimum in some codes, 120 PSI is the appropriate minimum test pressure. Other codes simply state 125 PSI or higher.
Why the other options are wrong
- B. Testing at working pressure is insufficient to detect potential weaknesses or leaks.
- C. 150 PSI would also pass, but 120 PSI is the minimum for this scenario.
- D. 100 PSI is below the typical code requirement of 1.5 times working pressure or 125 PSI.
Water System Pressure Test Criteria
Water distribution systems must be pressure tested at a specified minimum pressure, typically higher than the working pressure, for a set duration to ensure joint integrity and detect leaks.
- Required before final inspection and covering.
- Pressure typically 1.5 times working pressure or 125 PSI, whichever is greater.
- Test duration usually 15-30 minutes with no observable pressure drop or leaks.
Memory trick: Test at one-and-a-half times the Max, or One-twenty-five, whichever's more.