Test Header
The Flow Test Manifold
The array of 2½-inch outlets that lets you dump a fire pump's rated flow safely onto the parking lot — and prove the pump still makes curve.
Why Pumps Need a Test Header
NFPA 25 §8.3.3 requires an annual performance test of every fire pump: you need to move rated flow through the pump at rated pressure, then 150 percent of rated flow at not less than 65 percent of rated pressure, and verify the churn pressure against the acceptance curve. To do that you need somewhere to dump water.
A test header is a short branch piped off the fire pump discharge, typically exiting the pump room to an exterior wall, terminating in a row of three to six 2½-inch hose valves mounted in a weather-protected enclosure. During the test, inspectors attach hoses, open valves one at a time, and use pitot tubes on short playpipes to measure flow out of each hose. Multiple outlets are needed because a single 2½-inch hose line only carries about 500 gpm.
How to Read the Flow
Each open hose valve is measured with a calibrated pitot gauge placed in the center of the stream just outside the smooth-bore nozzle. The pressure reading (in psi) is converted to flow (in gpm) using the nozzle coefficient and discharge formula: Q = 29.84 · c · d² · √P. Add up each individual flow to get the total discharge, then plot it on the acceptance curve.
Alternatives — Flow Meters and Hydrants
Where a test header is impractical (roof-mounted pumps, urban sites with no drainage), NFPA 25 §8.3.7 allows alternatives:
- Flow meter on a test loop: water recirculates back to the suction supply through a calibrated meter. No water leaves the building. Accurate but expensive to install.
- Hydrant dump: discharge into a nearby hydrant-flow drain. Requires AHJ approval and coordination with the water utility to avoid brown-water complaints.
- Suction side flow measurement: rarely used because it requires a meter on the supply line that is always in service.
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Watch on YouTube →References
1. NFPA 20 (2022), §4.20 — Fittings for flow measurement.
2. NFPA 25 (2023), §8.3.3 — Annual fire pump performance test.
3. NFPA 25 (2023), §8.3.7 — Alternatives when a test header is unavailable (flow meter bypass, hydrant dump, etc.).
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Discussion (2)
Great breakdown of the technical details. The NFPA 25 maintenance table is exactly what I needed for my ITM schedule.
Really clear explanation. Would love to see a companion video walkthrough of the inspection process.