At what gauge pressure must all piping and appurtenances be hydrostatically tested?

The appropriate gauge pressure for hydrostatically testing all piping and appurtenances, as specified by NFPA 24, is 200 psi. This testing pressure ensures that the system can withstand operating pressures along with any added safety factors that might be necessary to account for possible weaknesses or imperfections in the system components.

At 200 psi, the test helps to identify any leaks or failures in the system that could pose a risk during operation. This level of pressure is considered adequate for ensuring the integrity and reliability of the fire service mains and their appurtenances prior to being placed into service. Conducting hydrostatic tests at this pressure not only validates the strength of the materials used but also ensures that the installation meets safety standards necessary for fire protection systems.

Lower pressures might not sufficiently stress the system to reveal potential issues, which is why 200 psi is typically mandated.