After completing a water supply system, at what pressure must it be tested?

The water supply system must be tested at a pressure that is at least the working pressure of the system to ensure that it can handle operational conditions without leaks or failures. This testing ensures the integrity and reliability of the plumbing system before it goes into service.

Testing at the working pressure simulates normal conditions that the system will encounter during its operational life. This is crucial for verifying that all joints, fittings, and materials are properly installed and that there are no weaknesses that could lead to leaks or other failures.

The other options, while they might suggest a rigorous approach to testing, do not align with the standard requirement that prioritizes verifying that the system functions well under the conditions it is designed to handle. Testing at pressures significantly above the working pressure may unnecessarily stress the system, while testing below the working pressure would not adequately assess the system’s ability to withstand normal use. Thus, adherence to the working pressure as the minimum testing standard ensures safety and effectiveness in the plumbing system.