Fire Pump Priming Basics - Part 2

Dominic Colletti reviews and offers solutions to common priming problems.

Fire pump primers may not be glamorous, but priming systems are critical to pump drafting performance. Pulling a prime quickly is key to fast water delivery, a basic fireground necessity. Last month, we answered several questions about pump priming. This month, we will continue our look at priming...

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Recommendations for each priming system vary by manufacturer. Ask for testing and maintenance information. Make priming system checks an integral part of your scheduled fire pump preventative maintenance and testing program. Failing to care for your priming system is foolish. If your priming system fails because of benign maintenance neglect, your engine could be useless the next time drafting is required. A few suburban departments have been lulled into a false sense of security because their fire districts have lots of hydrants and therefore they don't need to use the primer much.

While a priming system is an important fire pump accessory, it is often thought of secondarily when planning apparatus specifications, and not given adequate attention during pump testing and maintenance. Good priming system design, installation and maintenance are critical for effective drafting operations. Make sure your priming system, fire pump and pump operation training are up to par to prevent a fireground catastrophe.


Priming pump electric motor doesn't turn.

  • Dead battery
  • Main power feed wire has bad connections
  • Bad electric primer motor ground
  • Bad master disconnect switch or solenoid
  • Solenoid switch which activates primer is bad
  • Wiring to control solenoid had bad connections or is disconnected
  • Defective solenoid
  • Defective motor
  • Defective switch on priming valve

Vacuum priming pump is slow to pull a prime or priming maximum vacuum is lower than normal (vacuum holds).

  • Low charge on batteries
  • Batteries not sufficient size
  • Cable between battery and primer insufficient size
  • Electrical connectors on cable dirty
  • Bad ground
  • Extremely large quantity of suction hose or suction piping
  • Too small or too long a length of piping between primer and pump
  • Priming valve not fully opening (operator error)
  • Lift is too high
  • Primer vanes worn
  • Loose or broken V-belt (on belt driven primers)

Priming pump can pull some prime, but it will not hold vacuum.

  • Air leaks somewhere in the system
  • Bad suction hose gasket
  • Pump or discharge drain was left open
  • Gauge or drain tubing line disconnected
  • Leaking or stuck priming valve
  • Priming valve seat defective
  • Leaking suction relief valve
  • Rusted-out piping
  • Leaking suction hose
  • Bad mechanical seal
  • Leaking packing
  • Bad flange gasket on pump
  • Cracked or broken casting

Can pull full prime, it holds, but pump loses water when you start to pump, or pump cavitates prematurely, or pump cavitates at high pressures.

  • Pump impeller is damaged or severely worn out
  • Suction hose not submerged in adequate water supply
  • Air leak during water flow (see list directly above).
  • Clogged inlet strainer on pump suction hose
  • Pump impeller pre-rotation baffle is missing
  • Air pocket in piping or air trap in suction hose
  • Air accumulation in piping
  • Turbulence in piping
  • Too much vertical distance to water source and/or, too many lengths of suction hose
  • Failing (collapsing) suction hose

DOMINIC COLLETTI is the author of The Compressed Air Foam Systems Handbook and Class A Foam - Best Practice for Structure Firefighters. He is co-author of Foam Firefighting Operations 1 and The Rural Firefighting Handbook. Colletti is a former assistant fire chief and serves on the technical committee of NFPA 1500 Fire Department Occupation Safety and Health Program. He is the Global Foam Systems Product Manager for Hale Products and can be reached at