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Thread: Spa spillway: always on = high acid demand?

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    Spa spillway: always on = high acid demand?

    Hi! Is it normal that the spa spillway to the pool cannot be turned off when the pool pump is on?

    My pool's acid demand is very high even though the salt water chlorinator only runs at about 40% in the summer. I suspect the aeration from the spill-back (from the spa to pool) is the reason for the high acid demand.

    It seems like it would make sense to have a valve allowing for the spillway to be turned off. Mine only has the check valve, but no way to turn it off. Is this normal?


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    mas985's Avatar
    Join Date
    May 2007
    Pleasanton, CA

    Re: Spa spillway: always on = high acid demand?

    First, welcome to the forum!

    Yes, the extra aeration can cause PH to rise. Lower TA can help some.

    As for turning it off, it depends on your setup. If the valves are automated, then there is usually a way to do turn off the spillover with the controller. If you don't have a controller, then it might be possible with other valves but it doesn't sound like the PB set it up that way. It might be easier to take a picture of your pad equipment rather than trying to describe it.
    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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    Join Date
    Feb 2008
    Denton, TX

    Re: Spa spillway: always on = high acid demand?

    You may be able to install a valve that allows you to isolate the spillover. Along with what mas985 said, a picture would help us see what is what.

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    Richard320's Avatar
    Join Date
    Jan 2010
    San Dimas, CA (LA County)

    Re: Spa spillway: always on = high acid demand?


    My spa has a separate valve, so I reduced the flow to it and the pH rise slowed down considerably. And after a huge amount of rainwater dilution pushed the TA down to about 50, pH stayed fairly stable.

    Your pool will have its own personality, so you'll have to find your own "sweet spot" for TA.
    16K freeform gunite with spa; Pentair 4000 DE filter; Century Whisperflow 1 HP; Pentair Minimax heater.
    Troublefree does not mean Maintenancefree. It's like brushing your teeth: You can spend a couple minutes a day and pennies a week or go to the dentist once a year and spend several thousand dollars.
    A pool is like a pet - you have to feed it every day, even the days you don't want to play with it!

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    Re: Spa spillway: always on = high acid demand?

    Thanks for the feedback! I added a picture for clarification (sorry its blurry, its all I have at the moment). You can see on the left side of the picture a check valve for the spa spillover. Next to that, there is a hand valve. That hand valve can throttle the pool jets. When I close the hand valve, the pool jets shut off, and the flow over the spillway increases. When the hand valve is full open, water flows through the pool jets, but some water still goes to the spa and flows over the spillway.

    Unfortunately, there isn't much room to add a valve to turn off the spillway completely. Is it normal not to have a valve for shutting it off? Any other suggestions? Thanks again!

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