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Thread: System losing prime when pump is off

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    System losing prime when pump is off

    I have a Pentair/Hayward setup with sand filter. Thinking about adding a timer to my setup to run pump when needed. My question is when pump is turned off manually now, it loses its prime and when turned back on shoots dirty water back into pool. I guess when its losing prime its disturbing the sand bed??? I think from reading some of pool school it seems it is a pressure side leak? The strainer lid basket is tight. Could it be a gasket in the multiport valve itself?? When the pump is off, it seems you can hear water draining back into the filter almost as if the backwash setting is on and air can be felt coming out of the clear sight window. Any help would be greatly appreciated.
    31,000 Gallon Inground with Vinyl Liner. Dolphin M400. BBB METHOD. Liquid Bleach. Pentair Tagelus TA-60 Sand Filter

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    Mod Squad Bama Rambler's Avatar
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    Re: System losing prime when pump is off

    It sounds like it could be the spider gasket. Is there any water going out the backwash outlet when the valve is in filter mode?
    Dave J. TFP Moderator
    24' x 52" Round AGP. 2hp/¼hp SPL Power-Flo 2-speed pump. 200sqft Waterway Cartridge Filter. 45MHP2(3GPD) Stenner Peristaltic Pump
    Pool School ----- Pool Math ----- TF-Test Kit

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    Re: System losing prime when pump is off

    Not when in filter mode with pump on but with pump off in filter mode when i noticed air coming out of sight window, there was water trickling out of backwash pipe
    31,000 Gallon Inground with Vinyl Liner. Dolphin M400. BBB METHOD. Liquid Bleach. Pentair Tagelus TA-60 Sand Filter

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    Mod Squad Bama Rambler's Avatar
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    Re: System losing prime when pump is off

    That pretty much confirms that it's most likely the spider gasket.
    Dave J. TFP Moderator
    24' x 52" Round AGP. 2hp/¼hp SPL Power-Flo 2-speed pump. 200sqft Waterway Cartridge Filter. 45MHP2(3GPD) Stenner Peristaltic Pump
    Pool School ----- Pool Math ----- TF-Test Kit

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    Re: System losing prime when pump is off

    Can I tell by looking at it upon disassembly that its bad, or will i have to just replace it to see?
    31,000 Gallon Inground with Vinyl Liner. Dolphin M400. BBB METHOD. Liquid Bleach. Pentair Tagelus TA-60 Sand Filter

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    Mod Squad Bama Rambler's Avatar
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    Re: System losing prime when pump is off

    It's hard to say. From your description it appears to be holding at times so it may not be blatantly clear that it's bad. There should be indicators that you can see indicating that it's bad.
    Dave J. TFP Moderator
    24' x 52" Round AGP. 2hp/¼hp SPL Power-Flo 2-speed pump. 200sqft Waterway Cartridge Filter. 45MHP2(3GPD) Stenner Peristaltic Pump
    Pool School ----- Pool Math ----- TF-Test Kit

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    Re: System losing prime when pump is off

    OK I'll look. Thanks for your help.
    31,000 Gallon Inground with Vinyl Liner. Dolphin M400. BBB METHOD. Liquid Bleach. Pentair Tagelus TA-60 Sand Filter

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