Troubleshooting Tips


Loss of Prime




    The purpose of the loss of prime feature is to protect the pump and motor from damage that would be caused if the pump were operated without water.  If a pump were to lose prime and continue to operate with no water moving through the pump, the pump would develop heat, which would eventually damage the pump seal, motor, pipe manifold and related components. 


Possible Cause List

1.     Pump lost prime.

a)    For a pump to lose prime air must enter the system.  Find the source of the air.  A small amount of water leaking back through a check valve will not cause a loss of prime because no air can enter the system in this way unless the pump is off for weeks.

b)    Check for air leaks first at fittings easily accessible, and at the check valve connection.

c)    Intake screen missing allowing debris to interfere with check valve.  If the check valve sticks wide open you may hear a rush of water backwards if you open a hose bib.

d)    Leaking pump seal.


2.     Serious pump or motor problem.  When either of the two problems below occur a LOSS of PRIME alarm will be declared even though the pump has not lost prime.

a)    Pump impeller off shaft, usually involves broken or unscrewed center bolt.

b)    Broken pump shaft.


Air Lock

     Air lock occurs when the pump intake line has a high spot trapping air.  When an air lock occurs water flows underneath the air pocket.  The only way that an air lock can be removed (if at all) is to increase water velocity so that the air is “swept” downwards out of the high spot and on to the pump.  When air is pulled from an air lock the pump often loses prime.

      It is difficult to determine if a pump lost prime because of an intake line air leak or air came in from an air lock.  The technician will re-prime the pump and run water again.  If the pump loses prime again then the technician may re-prime and try it again.  At some point in this cycle of losing prime and re-priming the technician may wonder if the problem is an intake line leak or an air lock.

      The key diagnostic observation to make is that the technician may notice improvement, each time the technician re-primes the pump the pump will run water a little longer.  If improvement is noted then the problem is an air lock.  If the technician goes through many cycles and there is no improvement, then an air leak may be the cause.  Sometimes the cycle will have to be repeated many times before an improvement is noticed, especially on very long intake lines.


Learn More About Air Locks

Learn more about Intake Lines



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