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Thread: Check valve question

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    Join Date
    Feb 2011
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    La Quinta, CA
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    Check valve question

    I have an inground pool with built in spa at one end...the spa is about two feet higher than the pool surface. When the filter pump is on the water goes into the spa, over the edge, and into the pool then back to the filter pump. I run the pump 6 hours a day. By the next day the water level in the spa has dropped about 18 inches. When the filter pump starts up again for the day it takes about 15 minutes before the water level rises in the spa enough to spill the water into the pool. I have my re-fill float turned off. The water level in the pool stays the same after the filter pump is turned off. The pool/spa and equipment is about 5 years old. What causes the water level in the spa to drop after the filter pump is turned off? Is this a check valve problem and if I don't do anything to fix it will it cause any damage?

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    In the Industry

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    Re: Check valve question

    Yes it's a check valve issue.. Biggest problem if you don't fix it is going thru lots of fresh water and possible pumps running dry if water level wasn't checked for days..

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    Re: Check valve question

    Biggest problem if you don't fix it is going thru lots of fresh water
    ____________________________________________________________ ______________________
    How can the pool be using fresh water if the re-fill float is turned off?

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    mas985's Avatar
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    May 2007
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    Pleasanton, CA
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    Re: Check valve question

    As the spa level drops, the pool level will rise until the two meet at the same level. If you have an autofill on the pool, it should not add any more fill water as the pool level rises when the spa level drops. About the only issue I can see is that the spa has about 18" of the surface exposed and if it is plaster, then that could damage the surface if exposed too long.

    This problem can occur with a bad check valve but it can also occur if the return valve is positioned such that there is return path to both the spa and the pool. When the pump shuts off, water will then be siphoned out of the spa into the pool via the return pipes.
    Mark
    Hydraulics 101; Pump Ed 101; Pump/Pool Spreadsheets; Pump Run Time Study; DIY Acid Dosing; DIY Cover Roller
    18'x36' 20k plaster, MaxFlo SP2303VSP, Aqualogic PS8 SWCG, 420 sq-ft Cartridge, Solar, 6 jet spa, 1 HP jet pump, 400k BTU NG Heater

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    Feb 2011
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    Re: Check valve question

    Thanks for the info......I'll be replacing the check valve is that is the problem and/or making sure the return valve is set properly.

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    JasonLion's Avatar
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    May 2007
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    Silver Spring, MD
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    37,879

    Re: Check valve question

    If it is a check valve problem, and you have a better quality check valve, this is usually easy to fix. Usually this kind of problem is caused by something stuck in the check valve that is preventing it from sealing correctly. If you have one of the better quality check valves that can be opened up, you should take a look inside and make sure there isn't any debris blocking it from closing correctly.
    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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