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Thread: Confused about alkalinity and pH

  1. Back To Top    #1

    Join Date
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    Confused about alkalinity and pH

    So I have a slightly low alkalinity level - last test was about 80 ppm. Latest test results are:

    FC 4
    CC 0
    pH 7.5
    Calcium 200
    Alkalinity 80
    CYA 70

    I think need to bump my alkalinity up, so planning to add some arm and hammer shortly, to move it closer to about 95-100 ppm. Won't that throw my pH off though? Then I would add some muriatic acid, but won't that then drop my alkalinity back down again?

    #confused
    20000 gallon, IG, SWG, Sand Filter, Hayward 1/2HP + Lorentz direct solsr PV pump

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    Re: Confused about alkalinity and pH

    Why do you feel the need to change the TA?

    I'd be more concerned with your free chlorine level at 4 with 70 CYA, you need at least 6.
    16 x 32 17500 gallons
    Vinyl in-ground
    Hayward 250# Sand Filter
    1 HP Pump
    Hayward SWG

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    Re: Confused about alkalinity and pH

    What kind of pool do you have? Vinyl or Plaster?

    If your PH is stable I wouldn't change the TA. If you have a plaster pool you might want to add some calcium.
    16K Gal Plaster | Compupool SWG | Intelliflow VF | TF-100

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    Re: Confused about alkalinity and pH

    TA is sometimes called a buffer. It is there to help your pH from changing much. To low TA and you get quick pH changes. Too much and pH keeps raising itself. Get as much or little as needed for YOUR pool. A person with a SWG or operating water features will have different requirements than someone without etc.
    13k Pebbletec Pool/Spa, Hayward Ecostar, SGS Breeze 540 SWG, Pentair C&C 420 cartridge, Pentair MasterTemp Heater, Caretaker system, TF-100 & Taylor K1766 test kits

  5. Back To Top    #5

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    Re: Confused about alkalinity and pH

    Quote Originally Posted by Griswald View Post
    Why do you feel the need to change the TA?

    I'd be more concerned with your free chlorine level at 4 with 70 CYA, you need at least 6.
    Understood. Will bump SWG output to 50%.

    On the alkalinity, it was my understanding I am on the low end. But...if y'all think it is good, then I will go on this.


    68,000litre, IG vinyl, LorentzPS 600 Solar Pump & 1/2 HP Tristar, Sandfilter, Aquarite T-15 SWG
    20000 gallon, IG, SWG, Sand Filter, Hayward 1/2HP + Lorentz direct solsr PV pump

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    Re: Confused about alkalinity and pH

    Quote Originally Posted by lightingguy View Post
    What kind of pool do you have? Vinyl or Plaster?

    If your PH is stable I wouldn't change the TA. If you have a plaster pool you might want to add some calcium.
    Vinyl


    68,000litre, IG vinyl, LorentzPS 600 Solar Pump & 1/2 HP Tristar, Sandfilter, Aquarite T-15 SWG
    20000 gallon, IG, SWG, Sand Filter, Hayward 1/2HP + Lorentz direct solsr PV pump

  7. Back To Top    #7

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    Re: Confused about alkalinity and pH

    I typically add acid weekly or every ten days to keep it in the sweet spot. I don't think it swings too much, just a slow rise over a short period, which I understand is typical of SWG pools...


    68,000litre, IG vinyl, LorentzPS 600 Solar Pump & 1/2 HP Tristar, Sandfilter, Aquarite T-15 SWG
    20000 gallon, IG, SWG, Sand Filter, Hayward 1/2HP + Lorentz direct solsr PV pump

  8. Back To Top    #8

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    Re: Confused about alkalinity and pH

    Isn't the recommendation for TA to be from 60-80? Therefore you are more on the high side than the low side, according to here: Pool School - Recommended Levels

    I have a SWCG as well and I have always been fine running my FC closer to the minimum than the recommended levels. For CYA of 70 the min is 5 and the recommended is 8.

    Maybe I am wrong on this but I think those of us in cooler places with seasonal pools in places like Canada have less issues with algae and can live with lower FC, especially if your water is cooler.
    Vinyl 18'x36' in-ground 100,000 L, Jandy Aquapure 1400 SWCG, Jandy Lite2 heater, StaRite System3 filter, Evac tube solar heating panels

  9. Back To Top    #9

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    Re: Confused about alkalinity and pH

    Here we advise a lower TA because the types of chlorination we recommend tend to raise PH over time.

    If you were using TriChlor pucks you would want a higher TA as Trichlor is acidic.


    If it were me I would lower the TA to see if I could cut the PH rise down. You don't need to do this - it's just about convenience.
    16K Gal Plaster | Compupool SWG | Intelliflow VF | TF-100

  10. Back To Top    #10

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    Re: Confused about alkalinity and pH

    No, for CYA of 70 with a SWG, the recommended min FC is 3 with a target of 5 - see here.

    If your Ph is not rising too quickly, your TA is fine - if it does, then you can lower your TA to 70 and see if that helps. All of your other numbers look fine, too. You have a vinyl liner, so don't worry about CH.
    50,000 gallon plaster in-ground salt pool with two 60 sq ft DE filters, two Intellichlor IC60 SWGs, two Intelliflo VS pumps, two Whisperflo pumps, two Pentair 400K BTU NG heaters, PCC2000 in-floor cleaning system...two everything.

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