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Thread: pH still drifts

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    tedinelkgrove's Avatar
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    pH still drifts

    Fresh numbers:

    pH: 8.0
    TA: 80
    CA: 280
    Borates: 50
    FC: 6.0
    Temp ~75F

    pH drifts from 7.5 to 8.0 in less than a week. Do I go for a lower TA? This has been a constant issue. I keep waterfalls off 95% of the time. Wife turns them on when company is over. The 1.5hp single speed pump moves the water very well, almost aggressively if you get my meaning. You can see the water swirling all the time when it is on. I just want to be able to keep a constant pH of ~7.6 for a few weeks. Any more ideas?
    ~15000 gallon inground, plaster pool
    Jandy CL460 Cartridge Filter Tank, Jandy Stealth SHPF 1.5hp pump, Pentair Legend II cleaner
    Leslie's DPD Complete Test Kit, TF Tests FAS-DPD Chlorine Test Kit
    Heliocol solar pool heating (HC-40 x6)

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    JasonLion's Avatar
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    Re: pH still drifts

    Bring the TA down to around 60 and then see how things go. With borates in the water, you could even take TA down to 45 or 50.
    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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    Re: pH still drifts

    You could also make sure your returns aren't pointed too much upward. There shouldn't be too much of a rippling effect. You only need a gentle surface flow to get decent skimmer action -- if the water surface gets into little waves or breaks apart at the surface, then that will tend to increase the rate of carbon dioxide outgassing that causes pH to rise.

    When I want to intentionally force my pH to rise when I'm trying to lower the TA through acid addition and aeration, I generally point up my returns and set my pump on a high speed. That greatly accelerates the process so might be part of what is going on in your pool unintentionally.

    Of course, lowering the TA as Jason suggests should also help and you may need to do both -- lower TA and returns pointed out or slightly downward instead of upward.
    16,000 gallon outdoor in-ground 16'x32' plaster pool; Pentair Intelliflo VF pump; Pentair IntelliTouch i9+3s control system; Jandy CL-340 square foot cartridge filter
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    tedinelkgrove's Avatar
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    Re: pH still drifts

    Took pH down to 7.0, aerated with waterfalls and 3 days later TA is at 50 and pH about 7.5. If a TA of 50 stabilizes my pH, how do I offset the lower CSI value? I am about -0.4. Should I increase CH from 280 to 350?

    pH=7.5
    TA=50
    CYA=40
    CH=280
    Borates=50
    ~15000 gallon inground, plaster pool
    Jandy CL460 Cartridge Filter Tank, Jandy Stealth SHPF 1.5hp pump, Pentair Legend II cleaner
    Leslie's DPD Complete Test Kit, TF Tests FAS-DPD Chlorine Test Kit
    Heliocol solar pool heating (HC-40 x6)

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    JasonLion's Avatar
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    Re: pH still drifts

    Let the PH go up to about 7.7 and raise CH a little. Remember that you still want CSI to be at least a little negative.
    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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