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Thread: Continual declining ALK and increasing PH / 6k fiberglass pool

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    Continual declining ALK and increasing PH / 6k fiberglass pool

    I have a 6000ish gallon fiberglass pool. I chlorinate with 8% bleach and have done so for years. This year my alkalinity refuses to stay in the 100-110 rage that I try to keep it in and my PH always seems to move up to 8.0. I've never tracked CH but I just tested it and it is 40. Any suggestions? Water tastes somewhat salty. Should I just let the ALK drop down to where ever it wants to go? Any suggestions on what could be causing this?
    6000 gal inground fiberglass
    1.5hp pump / sand filter
    Liquidator

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    Mod Squad pooldv's Avatar
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    Re: Continual declining ALK and increasing PH / 6k fiberglass pool

    Yes, when PH gets to 7.9 or 8.0 lower it to 7.2-7.5 with muriatic acid. This will slowly lower your TA over time. At some point your PH should stabilize. It is fine to let your TA drop as low as 60.
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    2012 build and pics, 20k gal gunite, black onyx pebblesheen, OK flagstone, IntellifoVS, cart filter w/Pleatco, IC40 SWG, Solartouch, 5 12'x4' solar panels, HP50HA heat pump, 8mil solar cover, borates, TF-100 test kit, SONOS, Doheny's Discovery Robot, hot tub on bleach

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    Re: Continual declining ALK and increasing PH / 6k fiberglass pool

    Any idea what could be causing this shift? Old water? Weird bleach? I have never had this problem before. I have used almost 3 gallons of muratic acid this summer and that is a lot for a 6k fiberglass pool. I guess I will stop increasing the TA and just concentrate on the PH for a while and see where the TA ends up.
    6000 gal inground fiberglass
    1.5hp pump / sand filter
    Liquidator

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    Mod Squad pooldv's Avatar
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    Re: Continual declining ALK and increasing PH / 6k fiberglass pool

    Didn't catch that was a new this year problem in the first read. My first guess would be a TA change in the water supply. Have you tested your fill water? Maybe the TA is lower for some reason.
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    2012 build and pics, 20k gal gunite, black onyx pebblesheen, OK flagstone, IntellifoVS, cart filter w/Pleatco, IC40 SWG, Solartouch, 5 12'x4' solar panels, HP50HA heat pump, 8mil solar cover, borates, TF-100 test kit, SONOS, Doheny's Discovery Robot, hot tub on bleach

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    Re: Continual declining ALK and increasing PH / 6k fiberglass pool

    You may have more carbon dioxide outgassing occurring from greater aeration (including from summer rain), from higher temperature, from longer pump run times or more pool use (splashing, swimming), from more wind (if water gets churned), etc. Or you may have stopped using net acidic forms of chemicals such as Trichlor or Dichlor or non-chlorine shock. 100-110 ppm TA is on the high side for pools and there is no reason for you to try and keep it so high.
    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
    12 Fafco solar panels; Purex Triton PowerMax 250 natural gas heater (200,000 BTU/hr output); automatic electric pool safety cover; 4-wheel pressure-side "The Pool Cleaner"

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