3rd Year Electrical Trades Qualification (TQ) Practice Exam 2026 - Free Electrical TQ Practice Questions and Study Guide

The main idea is choosing a test pressure that reliably reveals leaks without overstressing the piping components. For gas piping runs that are 200 feet or longer, a test pressure of fifteen pounds per square inch is used. This level provides enough pressure to push gas through the entire long run so leaks won’t be hidden by the length of the line, while staying within safe limits for typical gas piping fittings and components. It’s also higher than normal operating pressure, so any drop during the test indicates a true leak rather than a test artifact. In practice, the system is sealed and pressurized to fifteen psi (usually with air or an inert gas, not natural gas), held for a specified period, and checked with a leak detector or soap solution for any pressure loss. If no leaks are found, the pressure is released and gas service is restored.