The purpose of this gauge is to conduct a "pressure test" on your gas pipe system after you have installed or modified it. This gauge is intended to detect a loss of pressure after you pressurize your system to 15 psi. For example, fit the gauge to your gas pipe system. Using the Shrader valve, add air to the system using a tire pump or air hose. Pressurize the system to 15 psi. Remove the air hose from the valve. Set a timer. If, after minutes, you can see a detectable drop in the pressure reading on the gauge, this indicates that the system is not holding pressure. Then you must locate and correct the leak. If after 30 minutes, there is no detectable loss of pressure, then you can consider it a pass. If we can help to provide you with more information, please give us a call. We are here from 8-5 Los Angeles time. (661) 257-3923. Ask for Jon or Dave.