Which of the following is an acceptable method for testing LP Gas piping systems for leaks?

Using a soapy water solution is an acceptable method for testing LP gas piping systems for leaks because it allows for a clear and safe visual indication of any escaping gas. When applied to areas where connections are made, the soapy water will create bubbles if there is a leak present. This method is not only straightforward but also minimizes the risk associated with more dangerous testing methods, such as using flame or fire.

The other methods presented do not provide the same level of safety or reliability. Using a match is dangerous and could result in a fire or explosion if gas is present. Relying on a pressure gauge alone does not indicate the presence of a leak; it only shows the pressure levels within the system. Lastly, a manual inspection might not detect small leaks effectively, as some leaks could be very subtle and go unnoticed without a tangible method like the soapy water test.