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Thread: Pump losing prime when shut off. Sucking sound from waste line.

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    Pump losing prime when shut off. Sucking sound from waste line.

    I recently opened my pool and have since discovered that my pump loses prime after it shuts off. (at night) It manages to re-prime itself so far but I am concerned at some point it won't. There is a sucking sound coming from the multi-port at the waste port and when I put my hand over it quits.

    I decided to plug the waste port and see if it maintains prime. So far it has. This seems odd because everything I have read says that any air entering the system must come before the pump. I am guessing there is a bad multi-port gasket but I am no expert.

    I have lubed and checked the pump basket lid gasket and it looks ok. I don't see any bubbles in the pot or in the pool. Anyone have any ideas if I am on the right track???

    multi port.jpg
    10,000 gallon
    Viking Freeform Fiberglass Inground Pool. FNS Plus DE Filter Pentair Challenger .75hp pump

    NC KANSAS44

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    JasonLion's Avatar
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    Re: Pump losing prime when shut off. Sucking sound from waste line.

    That is almost certainly a problem with the spider gasket in the multi-port valve. Replacing a spider gasket is usually fairly easy.

    Air in the pump strainer basket while the pump is running is a suction side air leak. But air while the pump is off could be a leak anywhere.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
    Creator of PoolMath and Pool Calculator. Other handy links: Support this site, TF Test Kits, Pool School

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    duraleigh's Avatar
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    Re: Pump losing prime when shut off. Sucking sound from waste line.

    This seems odd because everything I have read says that any air entering the system must come before the pump.
    Yeah, like Jason says, that applies only if the pump is running. I believe it to be the spider gasket as well.
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

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    Re: Pump losing prime when shut off. Sucking sound from waste line.

    Thanks for the replies and for confirming my suspicion. A couple of questions on spider replacement.

    I plan to order this gasket. http://www.amazon.com/dp/B0031U7AQI/...I3JZB3HC9RKIA2

    I've read different theories on adhesive for the gasket. Some say super glue. Some say use the blue RTV gasket maker stuff. Some say use nothing. I plan to order this as that seems to be the concensus? http://www.amazon.com/dp/B0002UEOKK/...IB8OS2K5&psc=1

    Sound OK?
    10,000 gallon
    Viking Freeform Fiberglass Inground Pool. FNS Plus DE Filter Pentair Challenger .75hp pump

    NC KANSAS44

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    JasonLion's Avatar
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    Re: Pump losing prime when shut off. Sucking sound from waste line.

    I'v never seen gasket maker used except when it is impossible to get an appropriate replacement gasket. You definitely don't want to use that as an adhesive.

    I recommend super glue. It makes it a little more difficult to remove the old gasket when it wears out, but otherwise gives the best results.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
    Creator of PoolMath and Pool Calculator. Other handy links: Support this site, TF Test Kits, Pool School

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