by Joan Leedy, Technical Director

The NFPA 11 Standard for Low-, Medium- and High-Expansion Foam, 2016 Edition, requires discharge testing including confirming the concentration of the foam solution during the commissioning a new foam system (Section 11.6.2). This would mean that all systems need to be flow tested and foam discharged. However, due to the environmental concern with foam discharges, section 11.6.3 allows for “listed or approved” methods that do not require foam discharge.

Furthermore, NFPA 25 Standard for the Inspection, Testing and Maintenance of Water-Based Fire Protection Systems, 2020 Edition, requires an annual operational test on foam proportioners which includes a foam sample to be taken and the concentration verified (Section NFPA allows for “simulated foam concentrates or alternative test systems” where allowed by the AHJ (Section

Two methods that do not discharge foam and are used extensively in the industry are:

Surrogate Liquids Test Method – A surrogate liquid is a non-foaming, environmentally-acceptable liquid specially formulated to simulate the flow characteristics of the foam concentrate. There are a number of different surrogate liquid formulations to match the viscosity characteristics of various foam concentrate products. This is especially true for alcohol-resistant foam concentrates where there can be substantial differences in viscosity and corresponding flow characteristics. For some new systems the surrogate liquid can be placed into the system foam tank, tested, and then rinsed prior to filling with foam concentrate. In many cases the foam tank is filled with foam so the surrogate liquid is placed in a portable bladder tank that is connected to the existing system using short fire hoses. In either case the system is discharged at the recommended flowrate and the proportioned stream is analyzed using on-line “real time” conductivity measurement instrumentation connected to a laptop data acquisition package. Similar to testing foam concentrate and water solutions, surrogate liquid injection rate is determined by making a reference curve indicating conductivity versus % concentrate that is used by the data acquisition system.  When testing existing systems, additional connections and the portable surrogate liquid bladder tank is required to allow the surrogate liquid to be directed to the proportioner in place of the foam concentrate.

Water Equivalency Test Method - In this method, water is used as the surrogate liquid. Acceptance tests must first be conducted with the actual foam concentrate, discharging the system and measuring the concentration using displacement, refractive index or conductivity. Once the foam concentrate meets the required concentration range, the foam concentrate is isolated from the system, and water is run through the proportioner in place of the concentrate at the same pressure and system water flowrate. The flowrate of the water being directed to the proportioner is recorded as the equivalency and this water flow rate is measured annually to ensure proper proportioning.

Both of these methods have been “certified” by an independent agency in the fire protection industry. These methods may be the AHJ’s preferred or required method for foam system acceptance and annual maintenance testing.

Here are two vendors offering alternatives to foam discharge testing:

If you have any questions regarding this article, please contact Dyne Fire Protection Labs at or (800) 632-2304.

©Dyne Fire Protection Labs 2020