Immediately before underground piping is placed into service, a hydrostatic test should be completed at ______ percent of the operating pressure but no less than ____ psig.

Immediately before underground piping is placed into service, a hydrostatic test should be completed at ______ percent of the operating pressure but no less than ____ psig.

• A. 100, 50
• B. 50, 150
• C. 150, 50
• D. 150, 15

Answer: (C)

During hydrostatic testing of underground piping, you stress the system beyond normal service to reveal leaks and weaknesses by filling it with water and increasing the pressure above the operating level. The requirement to use 1.5 times the operating pressure provides a margin that helps expose defects that might not show up at normal pressure. The minimum of 50 psig ensures the test is meaningful even when the operating pressure is very low, so the test isn’t conducted at an inconsequential pressure. So, the correct approach is to pressurize to 150% of the operating pressure, but not less than 50 psig. For example, if the system operates at 20 psig, you test at 50 psig (since 150% would only be 30 psig, which is below the minimum). If the system operates at 70 psig, you test at 105 psig, which is well above the minimum. This balance ensures both adequate stress and a reliable absolute pressure for the test.

During hydrostatic testing of underground piping, you stress the system beyond normal service to reveal leaks and weaknesses by filling it with water and increasing the pressure above the operating level. The requirement to use 1.5 times the operating pressure provides a margin that helps expose defects that might not show up at normal pressure. The minimum of 50 psig ensures the test is meaningful even when the operating pressure is very low, so the test isn’t conducted at an inconsequential pressure.

So, the correct approach is to pressurize to 150% of the operating pressure, but not less than 50 psig. For example, if the system operates at 20 psig, you test at 50 psig (since 150% would only be 30 psig, which is below the minimum). If the system operates at 70 psig, you test at 105 psig, which is well above the minimum. This balance ensures both adequate stress and a reliable absolute pressure for the test.