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Thread: Is It Normal For Pump To Stay Running For Hours When Dry?

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    Join Date
    May 2017

    Is It Normal For Pump To Stay Running For Hours When Dry?

    My pump has run dry several times. It's hard to avoid, because the pump is 6 feet above water level, so occasionally a twig or a bit of acorn will get stuck in the backcheck valve, and the pump will lose prime. Or, as happened the last time, I found the backcheck valve gasket shredded and the flapper mangled and warped (cavitation?). When this happens, I won't notice until the next time I go in the backyard when the pump is turned on and hear it sucking air. When I open the trap, the little bit of water in it will be scalding hot and steaming, and I've warped several trap baskets. Also, the plumbing on both sides of the trap (PVC glued with blue PVC cement) has sprung leaks, which I figure is probably due to the heat (does that sound right?).

    I've never seen the pump motor shut off because of this excessive heat, however. I figured the pump's heat protection circuit must be broken, but now that I am disassembling it, I'm not so sure. It doesn't look like the water is actually responsible for cooling the motor, which seems to be mostly air cooled, and the water only cools the pump itself. So, my question is, is it normal for the motor to run for hours with the pump dry and hot enough to melt lower temperature plastic, or does it seem like a bad pump motor? Is there any way I can keep the pump from running dry and wrecking things when the backcheck valve gets stuck open? I've bought a new, stronger backcheck valve, and I'm going to be replumbing everything from where the pool water pipe comes out the ground to the filter housing, and I'm replacing the pump's diffuser gasket (which had a break in it) and the shaft seal (which I've read will go bad if the pump overheats).
    20k Gallon In Ground Pool. Sta Rite P2RA5E-181L Pump w/ Marathon Electric 5KC38SN6084 motor. Hayward C1200 Star-Clear Plus filter. Rooftop solar heater. Pump ~6ft above water level.

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    Mod Squad jblizzle's Avatar
    Join Date
    May 2010
    Tucson, AZ

    Re: Is It Normal For Pump To Stay Running For Hours When Dry?

    Welcome to TFP!!!

    Hard to answer Yes or No.

    Yes, it is normal for a basic pump to just keep running dry and yes this will melt things. Some VS pumps have the ability to sense loss of prime and will shut off.

    But, No, it is not normal for a pump to lose prime in the first place. Even without a check valve on the suction line, the only way to lose prime is if you have an air leak in your system somewhere that allows the pump to drain when it turns off. Fix the air leak and you should not lose prime.
    Jason, TFP Moderator
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