Which of the following is true about hydrostatic testing before underground piping is placed into service?

• A. It must be performed at 150% of operating pressure with minimum 50 psig
• B. It must be performed at 200% of operating pressure with minimum 60 psig
• C. It must be performed at 120% of operating pressure with minimum 30 psig
• D. It is not required

Answer: (A)

Hydrostatic testing of underground piping is about proving the system can hold pressure and that joints and seams are sound before it goes into service. The correct approach uses a test pressure equal to 1.5 times the operating pressure, with a floor of at least 50 psig. This creates a safety margin that helps reveal leaks or weak connections without over-stressing the pipe. Higher test pressures aren’t required and can risk damage, while smaller pressures or skipping the test won’t reliably show whether the system would fail under normal use.