Part of receiving full credit for a "certified" static water supply in ISO's FDS is the inspection and flowtesting of those water supply sources. Many locales are moving to the use of large underground cisterns (tanks) as a means by which to provide strategically located, reliable water supply sites in rural areas. The 30,000-gallon tank is the minimum size recognized by ISO (250 gpm flow for 2-hrs). Part of a FD's water supply program must include the quarterly inspection and annual flowtesting of those tanks. The inspection is easy - complete a visual check for accessibility, damaged piping and fittings, signage, water tank level, etc...and of course, document that inspection.

For the flow test, you will need to establish a draft from the tank and flow water that can be measured (pitot gauge and chart). There is no time requirement regarding the length of the flowtest - but a reasonable practice is to flow for up to 3 minutes - that allows sufficient time for suction strainer issues to develop while minimizing the amount of effort needed to refill the tank at the end of the test. Many folks shoot for 1,000 gpm because that is the minimum fill rate for NFPA 1901 spec tankers. Also - many of the 30,000-gallon tanks use 6-inch suction pipe and fittings and those easily support a 1,000 gpm flow. Rember, once you are done flowtesting, be sure to refill the tank.