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Thread: Pump wont prime randomly

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    Pump wont prime randomly

    Im service tech. and i got called out to a house b/c a pump was not priming up when i got there I lubed the gasket it primed and got a new gasket b/c the old one was dry rotted. Worked for about a week now again didn't prime today. The pressure is relatively low in filter with full prime no visible leaks no visible blockage. Whats the next step?

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    bobodaclown's Avatar
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    Re: Pump wont prime randomly

    Welcome to the forums.
    It's getting air in the system someplace if it's not priming. You manually prime the pump, see if there air getting sucked into the basket, then use shaving cream or just use water around the lid, valves, and see if it makes a difference. Also check the weirs.

    When you wet the area and the air goes away you've found your leak.

    Did you wipe down/clean the seating area of the gasket you replaced?

    What the condition of the other pump seals?
    17K Kidney Shaped Pool Concrete (Diamond Bright) Pool, 3/4 hp 2 speed 115V Sta-rite Duraglas PEA5D-180L/P2R5D-181L (Impeller C105-92PS Diffuser C1-216P), 1.5 piping, Pentair CC100 Filter , Heat Siphon 100K BTU Heat Pump Pool Heater, Flow meter Blue White Flowmeter Model No. F-30150P, Hayward Astrolight SP0581N, SWCG CalimarTitanium Edition TE45 , Dolphin Nautilus Plus with CleverClean, Lakeland Florida

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    Mod Squad Bama Rambler's Avatar
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    Re: Pump wont prime randomly

    I concur about checking the skimmer weir(s) if it's an intermittent problem. If they stick once in a while it will cause the pump to suck air in and lose prime.

    Did you check to see if any air was getting into the filter when the pump is running?
    Is the pump basket full of water when it's running?
    Dave J. TFP Moderator
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    Re: Pump wont prime randomly

    Checked it out again and no air is getting into the system once fully primed. But, when the pump is trying to prime it will almost prime up then the water will drop out of the pump and repeat this over and over. Im guessing the impeller maybe slipping on the motor shaft but I dont know. Have you guys ever heard of that?

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    mas985's Avatar
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    Re: Pump wont prime randomly

    The nut in impeller can sometimes come loose and spin inside the impeller but usually it is not intermittent and would have the same issue after priming.

    A clogged impeller can also reduce the priming ability of the pump so either it won't prime or it takes a long time to prime.

    But per other recommendations, have you actually watched the weir/skimmer when the pump is starting to prime? If the water level is too low or the weir is stuck, the skimmer can suck in air to prevent priming but after it is primed, there may not be an issue. So just because there is no air entering the system after prime does not mean there isn't an issue at the skimmer. Just make sure.

    Also, once primed, is the filter pressure above or below normal operating pressure?
    Mark
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