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Thread: Can't keep pH down, losing a lot of FC, bubbles from the return, so confused!

  1. Back To Top    #1
    Bender's Avatar
    Join Date
    Dec 2013
    Phoenix, AZ

    Unhappy Can't keep pH down, losing a lot of FC, bubbles from the return, so confused!

    Summary: new (to me) pool, then did a drain, refill, SLAM (with success), here's where we are now:

    7/21 @ 19:56, ambient: 98f; water: 86f:
    pH: 7.5 (after adding ~32oz 14.5% MA an hour ago)
    FC: 4
    CC: 0
    TA: 120
    CH: 275
    CYA: 35 (!)

    My CYA has been holding at 50, I am shocked to see 35. I can't imagine that the auto-leveller replaced that much water in two days (I tested it 50 on the 19th, prior test was on the 14th when it was also 50). I will retest tomorrow in the sunlight (tested tonight indoors). Might be operator error.

    I am losing between 5.5 and 7.5 FC daily (bringing it up to ~11 every evening before bed). Pool gets zero shade while the crazy Phoenix sun is up (high today: ~110f).

    My pH is sitting around 7.8. If I add enough MA to bring it down to 7.3 it only comes down to 7.5 and a day or two later it's back to 7.8. TA doesn't seem to move at all by adding MA. Wanted to add borax but I don't see how that's ever going to happen if I can't move my TA down (I saw it down to 110 once directly after the SLAM on 6/11, otherwise it's always been 120-130).

    As of just today (didn't see it yesterday and we've been using the pool almost daily) I'm seeing lots of tiny, tiny bubbles coming out of two of the three returns. Not sure what this means but I'm sure it's not good.

    Cl additions seem to indicate (by the PoolMath calculator) that the pool is 6500gal based on the response (6.5 FC to 11 FC after sundown based on 44oz of 8.25%). My back-of-the-napkin math said 8200gal during the refill. But then: I added two bottles of the liquid CYA to bring the pool up to 30 which is what one bottle should have done. When I added solid CYA, the amount I computed (based on 8200gal) to bring me from 30 to 40 actually brought me to 50. So I'm not even sure what number to use for PoolMath at this point.

    Any thoughts? Enjoying swimming at least but frustrated with some of these issues.

    (Attachment is post-SLAM picture)
    Attached Images Attached Images
    ~12k gallon in-ground, Pebble Sheen, Hayward Pro-Grid D.E. filter, Pentair WhisperFlo, Zodiac MX8, TF-100 test kit

  2. Back To Top    #2
    Patrick_B's Avatar
    Join Date
    Jun 2011
    Midland TX

    Re: Can't keep pH down, losing a lot of FC, bubbles from the return, so confused!

    Welcome Bender!,

    Try not to be frustrated. pH rise is normal, and your fill water is replenishing the TA all the time. If you aren't getting to 7.3, simply bump the dosage up a little each time until you get the result you want. Having the pH bounce back is perfectly normal, so don't let it bother you. Start aiming for 7.2, and over a little time the TA will come down. Once it gets to around 80, the rise should slow a bit.

    Between the heavy use and intense sun your FC loss doesn't seem terribly high. It doesn't take a lot to impact a smaller pool volume like that, especially FC with people in the pool each day.

    Keep playing with the numbers on addition, and you'll figure out the sweet spot for all the chems you need to add.

    If you have consistent air coming back through the returns, it means there is a suction side air leak somewhere. Pretty common, and no, not good.
    TFP Moderator
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