NFPA 11 Acceptance Tests and ITM Under NFPA 25

A foam system should not be put into service until the numbers on paper have been proved on site. NFPA 11-2024 asks for that proof in Chapter 12 (acceptance testing) and hands inspection, testing and maintenance over to NFPA 25 in a single clause in Chapter 13. The foam-water sprinkler and spray chapter follows the same route: acceptance tests go to Section 12.9 and ITM to Chapter 13 (6.6, 6.7). This page walks through the acceptance tests, puts numbers on the proportioning tolerance and makes clear what NFPA 11 leaves to NFPA 25.

Clause numbers are from the 2024 edition, read from the standard's PDF pages. No copy of NFPA 25 was available for this page, so maintenance frequencies are not given here.

How Chapter 12 is organised

Chapter 12 has two layers. Sections 12.1 to 12.8 set out the acceptance steps common to all low-, medium- and high-expansion foam systems. Section 12.9 adds requirements specific to foam-water deluge and spray systems: flushing, hydrostatic testing, foam discharge, proportioning tests, instructions and signs.

Qualified personnel carry out the tests to the AHJ's satisfaction. The purpose is to show that the system matches the approved plans and specifications and works as intended (12.3).

Common acceptance steps (12.1–12.8)

1. Visual inspection (12.1): conformity with plans, continuity of piping, removal of temporary blinds, access to valves, controls and gauges, correct fitting of vapour seals where used; identification and operating instructions on devices.
2. Flushing (12.2): underground and aboveground supply mains are flushed at the highest practicable flow before connection to system piping, at no less than the system's water demand. All foam piping is flushed with the normal water supply with foam-making materials shut off. Where flushing is impossible, pipe interiors are inspected visually during installation. Compressed-air foam piping is flushed with the system's air supply instead of water.
3. Pressure test (12.4): all piping, except piping carrying expanded foam other than for subsurface application, gets a 2-hour hydrostatic test at 1379 kPa (200 psi) or 345 kPa (50 psi) above the maximum anticipated pressure, whichever is greater, in line with NFPA 13. Drainage pitch of normally dry horizontal piping is verified.
4. Operating tests (12.5): every operating device is function-tested. For total flooding systems, automatic closers on doors, windows and conveyor openings, equipment interlocks and automatic opening of vents are proved. Electrical control circuits and supervision are fully checked. The main drain is opened and static and residual pressures recorded. Every control valve is fully closed and reopened under system pressure.
5. Discharge tests (12.6): flow tests are run where conditions permit. Solution concentration is verified by digital refractometer, digital electrical conductivity, listed digital flow meters or another method acceptable to the AHJ. Records include static pressure, residual pressure at the control valve and at a remote reference point, actual discharge rate, consumption of foam-making material and solution concentration. The proportioning system may also be tested by a listed or approved method that does not discharge concentrate (12.6.4).
6. Paperwork and restoration (12.7, 12.8): the installing contractor notifies the AHJ and owner of the test date, performs the tests and completes and signs the material and test certificate. Afterwards the system is flushed and returned to service.

Proportioning tolerance: −0 % / +30 % or +1 point

The induction rate, expressed as a percentage of total solution flow (water plus concentrate), must be within −0 % to +30 % of the manufacturer's listed percentage, or within +1 percentage point, whichever is less (12.6.5, 12.9.4.1.4). There is no allowance on the low side: any result below the listed percentage fails.

For low-percentage concentrates the 30 % rule governs; for 6 % concentrate the one-point rule does. For positive-pressure proportioning with pumps or pressure-controlled bladder tanks, the percentage at minimum listed flow must not exceed the manufacturer's maximum percentage plus 30 % or 1 point, whichever is less (12.9.4.1.4.3). Variable-orifice proportioners use the same −0 % / +30 % or 1 point band (12.9.4.1.4.4).

Foam-water deluge and spray systems (12.9)

Flushing and hydrostatic test

Underground mains and lead-ins are flushed to NFPA 24 before connection (12.9.1). All piping, including concentrate lines, is tested hydrostatically at 13.8 bar (200 psi), or at 3.5 bar (50 psi) above the maximum static pressure where that exceeds 10.3 bar (150 psi), and the pressure must hold without loss for 2 hours (12.9.2.1). Bladder tanks are not included in pressure tests (12.9.2.1.2). The annex suggests holding test pressure with a small pump and the main control valve tightly shut, so that a break cannot cause serious water damage, and recommends testing concentrate lines with concentrate as the medium.

Foam discharge test

The test must show the hazard is fully protected in line with Chapter 4 and establish flowing pressures, actual discharge capacity, consumption of foam-making materials, staffing needs and other operating characteristics (12.9.3.1.2). It covers discharge from a single system and simultaneous discharge from the largest number of systems expected to operate on one hazard (12.9.3.1.3), and continues until discharge has stabilised.

Proportioning test: at which flow?

• Closed systems (wet, dry, preaction): concentration is verified at the calculated demand of the least hydraulically demanding condition and at the system's minimum design flow (12.9.4.1.1). A minimum-flow test equal to the flow of the four most remote sprinklers is also required (12.9.4.1.1.2), run at the low end of the proportioner's listed flow range (12.9.4.1.4.6).
• Open deluge systems: 12.9.4.1.1 names the mid-range design flow, while the very next clause, 12.9.4.1.1.1, names the actual calculated demand. Both sit side by side in the same edition, so settle which applies with the AHJ in the test plan.
• Pressure at the proportioner during the test is the system's design operating pressure (12.9.4.1.2).
• Full-flow testing of the proportioning system and discharge device is required to evaluate the proportioner properly (12.9.4.1.4.1). Balanced-pressure and positive-pressure systems may be tested through the test connections required by 6.4.10; other types need full-flow testing (12.9.4.1.4.5).
• Test solution is collected and disposed of as the AHJ requires. Solution collected in a clean container may be reused once to preprime the system if it meets the design criteria. With AHJ approval, simulated concentrates or alternative methods may replace real concentrate, but pressures and flows stay as specified (12.9.4.1.5–12.9.4.1.7).
• Solution flow is calculated from recorded inlet or end-of-system pressure; concentration by refractometer, conductivity or another approved method (12.9.4.2). Deluge and spray systems run with foam are flushed with water afterwards; parts normally holding concentrate need not be (12.9.4.3).

Foam quality: an informative benchmark

Annex A gives an informative table for foam from foam-water discharge outlets (Table A.12.9.3.1): protein and fluoroprotein foam at 3:1 to 8:1 expansion with a minimum 25 % drainage time of 15 seconds, and AFFF at the same expansion with a minimum of 60 seconds. Values are measured by the method in NFPA 11 Annex D; results from different methods are not directly comparable.

Handover: instructions and signs

• Instructions (12.9.5): the manufacturer's operating and maintenance literature, piping layout drawings, electrical schematics and hydraulic calculations, and a copy of NFPA 25.
• Hydraulic design sign (12.9.6): at every riser, floor control assembly, alarm, dry pipe, preaction or deluge valve; location of design areas, density, flow and pressure of the most and least demanding calculations, foam solution discharge duration, hose allowance and installer's name.
• General information sign (12.9.7): the information needed for ITM under NFPA 25; the last item on the list is the foam concentrate type and percentage.

The sample material and test certificate (Figure 12.9.3.1.1) asks separately for high-flow and low-flow proportioning results, disposal of test solution and whether simulated concentrate was used.

Chapter 13: maintenance goes to NFPA 25

Chapter 13 of NFPA 11-2024 is one clause: the owner or their authorised representative inspects, tests and maintains the foam system in accordance with NFPA 25 so that it keeps providing a reasonable degree of protection for life and property (13.1). Inspection frequencies, the annual concentrate test and proportioner testing details therefore live in NFPA 25, not NFPA 11.

The maintenance-related hooks left in NFPA 11 are these: the concentrate listing must publish acceptable ranges for density or specific gravity, pH, refractive index and viscosity, used to judge the concentrate test under NFPA 25 (4.3.1.4); a copy of NFPA 25 is handed to the owner (12.9.5); and the general information sign carries what NFPA 25 work needs (12.9.7). NFPA 25 frequencies for foam systems are outside the sources of this page and are not given here; confirm them against the current edition of NFPA 25.

For the design side see Foam-Water Sprinkler Systems; for proportioner types, NFPA 11 Concentrate Supply and Proportioning; for testing after a concentrate change, AFFF to F3 Foam Transition.

Frequently Asked Questions

What is the NFPA 11 tolerance on foam proportioning at acceptance?

The induction rate must be within −0 % to +30 % of the listed percentage, or within +1 percentage point, whichever is less (12.6.5, 12.9.4.1.4). For a 3 % concentrate that is 3.0–3.9 %.

At what pressure is a foam system hydrostatically tested?

Generally for 2 hours at 1379 kPa (200 psi) or 345 kPa (50 psi) above the maximum anticipated pressure, whichever is greater (12.4.1). For foam-water deluge and spray systems, 13.8 bar, or static plus 3.5 bar where static exceeds 10.3 bar, held for 2 hours without loss (12.9.2.1).

Is the bladder tank included in the pressure test?

No. Bladder tanks are excluded from the hydrostatic test of foam-water deluge and spray systems (12.9.2.1.2).

Does NFPA 11 set periodic maintenance for foam systems?

No. Chapter 13 passes inspection, testing and maintenance to NFPA 25 in one clause, with responsibility on the owner or their authorised representative (13.1). Clause 6.7 points foam-water systems to the same chapter.

Can simulated concentrate be used in acceptance testing?

Yes, where the AHJ approves, provided system pressures and flows stay as specified and meet the manufacturer's requirements (12.9.4.1.7). The proportioning system may also be tested by a listed or approved method that does not discharge concentrate (12.6.4).

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