water flow problem?

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[clover]

It sounds like you are describing "cavitations" where the pump, on high, is sucking air in, cavitating, and losing prime every 15 seconds.  This could be caused by a sticky filter weir gate restricting rapid water flow into the filter area, or it could be just a slightly low water level causing the same affect.  It sounds like your filter is running out of water faster than it can draw water in.

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[Chas]

Look in the motor compartment for valve such as these - they can sometimes begin to close by themselves. In fact, the one in the picture IS shown in the semi-closed position.



Otherwise, change the water.

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[ejf The Spa Guy]

it is nice to hear you found the problem.....