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Fire pump flow testing without hoses

NFPA 25 requires an annual flow test on every fire pump. A clamp-on meter on the discharge riser gives you the flow figure without hose streams, without a test header, and without dumping thousands of gallons across a parking lot.

Ultra ProLite
DN25–DN600
0.4″1″2″6″12″24″40″
Nominal bore, log scale. Both meters clamp to the outside of the pipe — nothing is cut, drilled or shut down.

Why contractors switch to clamp-on for the annual test

The traditional options are a hose-stream test with pitot readings, or a permanently installed flow meter loop. Both work. Both are also slow, weather-dependent and, in the case of hose streams, increasingly awkward where discharging potable water into a storm drain is restricted.

A clamp-on meter reads flow through the pipe wall on the discharge side. You get churn, rated and 150% flow points from the same sensor position, logged, without a drop of water leaving the system if you are testing through a closed-loop test header.

Ultra ProLite taking a flow reading on a red painted fire main with transducers strapped in place
Reading a fire main. Sound paint is fine to clamp over; loose rust and thick flaking coating get brushed back first.

What you need to know before you book

  • Pipe material and wall thickness. Steel riser is straightforward. Cement-lined ductile needs the lining thickness entered, and getting that wrong is the single most common source of a bad reading.
  • Straight run. Ten diameters upstream and five downstream, clear of the check valve, OS&Y and any elbow. Pump rooms are tight, so identify the measurement point before test day.
  • Water condition. A riser that has sat still for a year may have loose scale or air. Run the pump for a few minutes before you trust the reading.

Sequence on the day

  1. Pick the measurement point on the discharge riser and mark it. Clean the pipe surface down to bare metal or sound paint.
  2. Enter pipe OD, wall thickness, lining and fluid. Apply coupling gel and clamp the transducer pair on the rail.
  3. Check the signal strength and the measured sound speed against the expected value for water at that temperature. If sound speed is off, the wall thickness entry is usually the reason.
  4. Record churn, then each flow point as the test valve opens. Log the whole run rather than writing down spot values.
  5. Export the log by USB for the test report.

What this does not replace

The meter gives you flow. Suction and discharge pressure still come from your gauges, and the pump curve comparison is still your judgement. It also does not exercise the hose valves, which some AHJs will still want to see.

Can a clamp-on meter be used for an NFPA 25 annual fire pump test?
Yes. NFPA 25 requires the flow to be measured but does not mandate a specific instrument. A clamp-on ultrasonic meter on the discharge riser is widely accepted. Confirm with the authority having jurisdiction if you have not used one on that site before.
Do I still need to flow water through hoses?
Not for the flow measurement itself. If your test arrangement uses a closed-loop test header, the meter reads the flow without discharging. Some AHJs separately require hose valves to be exercised.
Which meter do I need for a fire pump test?
The Ultra ProLite at $699 per week covers typical 4 to 10 inch fire pump risers and is light enough to carry into a pump room.
How far from the check valve do the sensors need to be?
Ten pipe diameters upstream of the sensors and five downstream, clear of the check valve, control valve and any elbow. On a 6 inch riser that is 5 feet of clear pipe before the measurement point.

Get the meter on site this week

Request a rental quote(832) 899-4040