To Flow or Not to Flow

The forward flow test has been a requirement in NFPA 25, the Standard for Inspection, Testing, and Maintenance of Water-Based Fire Protection Systems, since its inception in 1992.

9-6.2.1*Backflow Devices. All backflow devices installed in fire protection water supply shall be tested annually at the designed flow rate of the sprinkler system, including hose stream demands if appropriate, and the friction loss across the device measured and compared to the device manufacturer’s specification. NFPA 25 (1992)

However, not many are aware of this requirement or how to conduct a proper test.  First, we begin with why the test is required.  It is an easy concept, the reason for the forward backflow test, is to ensure that the check valves within the backflow assembly will open when needed.  The actual backflow test  is done to determine if the check valves are  leaking our clean sprinkler water into the dirty drinking water. The forward flow and the actual backflow test (as required by XXX) are two separate and completely different tests. A required means to perform these tests has been required since the 1996 edition of NFPA 13.

4- Backflow prevention valves. Means shall be provided downstream of all backflow prevention valves for floor tests at system demand. NFPA 13 (1996)


Very seldom is there an adequate means installed to properly conduct the test.  The most common solution is to drain the entire system, turn the fire department connection (FDC) check valve around and flush through the FDC.  This is very time consuming and, in many cases, the FDC check valve is buried in a wall or other part of the building with little or no access. In later editions of NFPA 13, the requirement for a means to conduct the forward flow test was expanded on. The arrangement required in shall be serviceable without requiring the owner to modify the system to perform the test.  NFPA 13 (2019)

Annex section A16.14.5.1 states that a bypass around the check valve in the FDC line with a control valve in the normally closed position can be an acceptable arrangement. If a means to conduct the forward flow test is available, the test is very simple and should only take a few minutes. When a means to conduct the test is not available is where things can get a little confusing.  NFPA standards states, that when a means is not available, the inspector should open all possible outlets to conduct the test. This could be yard hydrants, fire pump test headers or drain valves.  This could also mean opening all drain valves at the same time to flow the system demand or as much as possible.  In light hazard occupancies, sometimes the main drain valve is sufficient to conduct the test. The real question is how do we determine that total system demand is being flowed?  There is no real requirement to measure the flow.* All backflow preventers installed in fire protection system piping shall be exercised annually by conducting a forward flow test at a minimum flow rate of the system demand. NFPA 25 (2020)


This has been a debate for many, in the sprinkler industry.  NFPA 25 does not require the measurement of flow but how does one prove they have flowed system demand?  It is a grey area, and one that many contractors have taken upon themselves to deal with differently depending on their experience with litigations. Some will measure the flow, some will not, both can be correct. NFPA standards are minimum requirements, nothing says that the flow cannot or should not be measured. Where connections do not permit verification of the forward flow test at the minimum flow rate of system demand, tests shall be conducted at the maximum flow rate possible. NFPA 25 (2020)

The annual test of the backflow preventor itself is not a requirement of NFPA 25. The forward flow test is and many times the annual test of the backflow is sold with the sprinkler system inspection and testing service, but the forward flow test is overlooked.  It is a simple test that is typically not completed by contractors and rarely enforced, yet it can have catastrophic results if the check valves in a backflow do not operate when the sprinkler system demand is needed. The results can be the same as a partially or fully closed control valve. Like all flow tests required by NFPA 25, they cannot be set aside until there is a fire to find out the systems have not been tested.