NFPA 16: Standard for the Installation of Foam-Water Sprinkler and Spray Systems Practice Test

Bladder tanks are excluded from hydrostatic pressure tests because the test is meant to verify the integrity of the water-filled piping and components under pressure, not the foam concentrate reservoir itself. The bladder inside the tank separates water from foam concentrate and is not designed to withstand the same hydrostatic loads as the piping. Subjecting the bladder tank to hydrostatic testing can damage the bladder, seals, or diaphragms and give a false sense of system integrity. Instead, bladder tanks are inspected and tested separately to verify proper precharge, condition of the bladder, foam concentrate supply, and the foam-proportioning function.