Final answer:
The proper test pressure for a gas piping system should exceed the normal operating pressure and is often determined by applying a factor of 1.5 or higher according to local codes and safety standards. The duration for holding the pressure typically ranges from 15 minutes to several hours, depending on the system's size and integrity requirements.
Step-by-step explanation:
The question you're asking pertains to the test pressure and duration required for testing a gas piping system with a 150' longest measured run and a system supply pressure of 7" water column. Generally, the test pressure for a gas piping system should be high enough to ensure the detection of any leaks but not so high as to cause damage to the system components. While the specific test pressure and duration can vary based on local codes and standards, a common approach is to pressurize the system to a level higher than the normal operating pressure, often by a factor of 1.5 or higher, and hold it for a sufficient duration to complete a thorough inspection, typically ranging from 15 minutes to several hours.
In this scenario, because you mentioned a system supply pressure of 7" water column, the test pressure should exceed that value, but the exact pressure should be determined in accordance with relevant safety standards and engineering practices. You should consult local regulations, codes such as the International Fuel Gas Code (IFGC) or National Fuel Gas Code (NFPA 54), or a licensed professional to determine the precise test pressure and duration for your specific gas piping system.