Main drain testing is the most fundamental test required by the National Fire Protection Association’s NFPA 25, Standard for the Inspection, Testing and Maintenance of Water-Based Fire Protection Systems. The stated purpose is “to determine whether there has been a change in the condition of the water supply.” Detailed information about testing requirements and methods can be found in NFPA 25-2011, 13.2.5 and A.13.2.5.

Testing must be performed on an annual basis and after reopening a valve. Since the 2002 edition, NFPA 25 has required quarterly testing of at least one main drain downstream of systems where the sole water supply is through a backflow and/or pressure-reducing valve. The NFPA 25 definition of annual frequency is “occurring once per year with a minimum of nine months and maximum of 15 months.” This may be further defined by the authority having jurisdiction.

In the past, testing was performed at each riser, but recent editions have reduced required testing locations. Language was added to the annex of the 2011 edition and later to the body of the 2014 edition that stated testing should be performed “for each water supply lead-in to a building water-based fire protection system,” eliminating the base of riser requirement. This definition includes both sprinkler and standpipe systems.

Interpretation of results should be a collaboration between the entity performing the testing and the facility staff. All measurements should be considered, including static pressure, residual pressure, return pressure, time to return and the conditions of testing. Any inability to safely discharge water should be noted, including the use of a fire hose, as this may shorten the test and provide inaccurate readings. Residual pressure readings should be compared to acceptance testing results, if available, as well as recent results. Simply comparing results to the prior year could result in an unwanted bias. Finally, a reduction in test results greater than 10% requires an investigation into the cause and correction if necessary.

The main causes for fire protection system failure are closed valves and water not reaching the fire. When designing and implementing a program, it is important to consider the intent and purpose of main drain testing. 

Chris Ribando, CET, is vice president at Approved Fire Prevention Corp.