The National Fire Protection Association (NFPA) 25-2014, section 188.8.131.52.9 states: “Dry pipe systems shall be tested once every three years for gas leakage.” This can be hard to convince building owners, especially if the system appears to be holding fine, no leaks are observed, and the air compressor is not running excessively.
The reason behind the requirement is to ensure there are no major problems. It also protects the building owner and the residents. The test, as stated in the NFPA 25 handbook reads: “Dry pipe systems that have excessive leakage can become costly for owners who constantly have to drain dry piping that becomes inadvertently filled.” This three-year leakage test ensures the system does not trip including instances where the air compressor is offline such as during a power outage.
This provision was added to NFPA 25 in 2008. Prior to 2008, NFPA 25 allowed a 10 psi pressure loss per week; however, this loss was difficult to detect because the air compressors made up this loss. The provisions of section 184.108.40.206.9 outline two options for testing for gas leakage and give a concrete way to determine if the system is leaking excessively. This section reads as follows:
220.127.116.11.9: “Dry pipe systems shall be tested once every three years for gas leakage, using one of the following test methods:
(1) A gas (air or nitrogen) pressure test at 40 psi (3.2 bar) shall be performed for two hours.
(a) The system shall be permitted to lose up to 3 psi (0.2 bar) during the duration of the test.
(b) Gas leaks shall be addressed if the system loses more than 3 psi (0.2 bar) during this test.
(2) With the system at normal system pressure, the gas source (nitrogen supply, compressor, or shop air) shall be shut off for four hours. If the low-pressure alarm goes off within this period, the leaks shall be addressed.”
For further information or questions, consult with the National Fire Protection Association.