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Thread: Pool pH keeps rising. Could it be the returns in my spa?

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    Join Date
    Mar 2016
    Portland, TX

    Pool pH keeps rising. Could it be the returns in my spa?

    Hello all,
    First post here and first time pool owner. I purchased a home with an existing 24k gallon IG plaster pool in south Texas. This pool is L shaped and has a small spa located on the inside of the L as you can see in this photo. The plumbing is connected for both. My math says the pool and spa make about 24.8k gallons combined.
    2016-04-03 18.58.36.jpg
    We emptied the pool completely and gave it an acid bath last week. I've since refilled and slowly getting my numbers right. Here is what I have right now.

    FC 8 - Will be keeping around 6.
    CC 0
    TA 100
    CH 150 - Will be receiving 25LB of Calcium Plus from Robelle tomorrow.
    pH 8.0
    CYA 35 - Still adding dry cya in a sock. Goal is 50-60.

    I've noticed my pH continues to rise from 7.5 to 8.0 daily. I bring it back down to 7.5 with 24oz of 31.45% MA and it jumps right back up the next day. I have a theory that my spa returns are causing aeration. They have a ton of bubbles coming from them.
    2016-04-07 11.00.38.jpg
    The returns for the pool don't have this problem. Any ideas? The spa has 3 returns and the pool has 2. I have not yet found a way to turn them off separately. Where could the air be coming from? I have a pipe coming out of the ground the seems to be sucking some air.
    2016-04-07 10.58.50.jpg
    Is this the source? I covered with metal tape to test and still had bubbles. Any ideas? Thanks in advance.
    24k IG plaster "L -shaped" pool with 6'x6' square spa, Hayward S210T Sand Filter, Hayward 1 HP pump, Polaris 280 cleaner with 3/4 HP pump, City Water, Taylor K-2006 kit

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    Mod Squad JVTrain's Avatar
    Join Date
    Feb 2014
    Central Minnesota

    Re: Pool pH keeps rising. Could it be the returns in my spa?

    Your TA is marginally high so as you continue to maintain your pH that number will come down. Higher TA results in faster pH rises with aeration. Each time you add acid, your TA will decrease.

    As far as the bubbles in your spa returns, many pools with a spa have a blower accessory that intentionally adds air to your returns that feed the spa. Do you have a blower? If so you may be able to bypass or turn it off, except for when you are going to use the spa. A wider shot of all your pool equipment on the pad may help.
    Joel - TFP Moderator - Minnesota - **Become a TFP Supporter!** Helpful Links: ABCs of Pool Water Chemistry - SLAM Procedure - Chlorine/CYA Chart
    40x20 Pool: 32K Gallons * Vinyl * Bleach Chlorination * Hayward S270T Sand Filter * Pentair SuperFlo 1 HP * Teledyne/Laars Heater * AquaVac Tigershark * TF-100 w/ SpeedStir
    Isolated Spa - 345 Gallons

  3. Back To Top    #3
    Richard320's Avatar
    Join Date
    Jan 2010
    San Dimas, CA (LA County)

    Re: Pool pH keeps rising. Could it be the returns in my spa?

    What you describe sounds pretty normal. High TA will drive pH up very fast especially with a lot of aeration.

    If your system isn't automated, somewhere there should be some three-way valves to select the pump intake and outlet. Look around your pump and filter for any labelled pipes, or start experimenting to see what does what on the valves.

    I cut the spa return down to almost nothing and have no suction from the spa under normal conditions. I also have an air intake like yours. I capped it with the lid from a can of spray paint. It reduces the bubbles a huge amount. Spa jets are designed to aerate, so you'll never eliminate all of it, but you can reduce it. As you keep adding acid, you'll notice that it takes less and less acid to get the same effect and you can go longer and longer between additions. That's because the TA goes down some with each pH adjustment and it stays down, even though pH rises again.

    If it's really becoming an annoyance, aggressively lower TA. In that case, you'll want maximum aeration - spa blasting fully, pool returns pointing up. Once TA is down below 70, then you can reduce the spa flow and cap the air and set everything back the way it was.
    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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