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Thread: adjusting TA and PH - geenral approach

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    Diver's Avatar
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    adjusting TA and PH - geenral approach

    Hi!

    I’m a new pool owner (old pool, new owner ). I bought a house last August and maintained the pool for about a month before I closed it for the winter. I’ve been educating myself on the pool maintainance subject for a while to make sure I know what I’m doing for the coming pool season.

    One question that I’m not crystal clear is the order of adjustment for TA and PH. I understand what they are and the relationship between them and read as much as I could but still there doesn’t seem to be a consensus on this topic. There are several posting on this subject in this forum but that seem to answer a specific situation rather than a general approach.

    Here are my thoughts:

    TA low, PH off – adjust PH first and then “fix” it in the range by brining TA up. Problem with this could be troubles adjusting PH since it might go up and down wildly since TA is low. Alternative would be to bring TA to the range, then adjust PH. Problem with that it could be difficult to adjust PH since it would be stabilized by TA being in proper range.

    TA high, PH off – adjust TA down first to allow for PH to be adjusted, adjust PH then. This seems to be logical, since it would be very difficult to adjust PH if TA is too high, so it seems like there is no choice here. Again I still see the problem with adjusting PH if TA is normal as in case above.

    I’m somewhat inclined to adjust TA first and then change PH if adjusting PH is not too difficult when TA is ok. Opinions on this forum and internet in general vary, but I would love to hear some pros and cons for both cases.

    Thank you!

    P.S. I know that chemicals for adjusting might affect both, but that can be accounted for. For the sake of discussion let assume that adjustments are 100% independent.
    26K In-ground Vinyl Pool | Hayward DE4820/SP0710XR50 filter | 1.125 HP Dual Speed Hayward Super Pump | Aquasol Solar

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    JasonLion's Avatar
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    Re: adjusting TA and PH - geenral approach

    There are lots of special cases if you want to do things in the very most efficient way. But the following rule will always be good enough, if not perfect:

    If TA is below 50, raise TA to 50 first.
    Then adjust PH except:
    * If TA is too low adjust PH to 0.1 or 0.2 lower than your target
    * If TA is too high adjust PH to 7.2
    Finally, adjust TA further
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
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    Diver's Avatar
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    Re: adjusting TA and PH - geenral approach

    JasonLion,

    Thanks for the quick response. I'm in no way questioning your suggestions, just trying to understand it better. So..

    > If TA is below 50, raise TA to 50 first.

    this makes sense. very low TA will make PH adjustments very difficult since PH will move up and down a lot

    > If TA is too low adjust PH to 0.1 or 0.2 lower than your target

    is this the case when TA is raised by soda ash that increases PH? what if baking soda is used for TA up? my understanding is it will not raise the PH. should PH still be adjusted first before adjusting TA?

    > If TA is too high adjust PH to 7.2

    wouldn't it be very difficult?

    TA adjustment should follow with a full pool recirculation before new tests are performed. That's at least 6-8 hours.Is is also the rule for PH adjustment?
    26K In-ground Vinyl Pool | Hayward DE4820/SP0710XR50 filter | 1.125 HP Dual Speed Hayward Super Pump | Aquasol Solar

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    JasonLion's Avatar
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    Re: adjusting TA and PH - geenral approach

    I am assuming you are using baking soda to raise TA, borax to raise PH, and muriatic acid to lower PH. Lowering TA is a whole project, not covered here (see the article in pool school).

    If you are using soda ash to raise PH then it will affect the TA a fair bit and there are more special cases.

    Baking soda will raise the PH quite a bit if the PH starts really low. Otherwise the effect of baking soda on PH is minimal, though never zero.

    Any adjustment to either PH or TA will affect the other to some extent. In most cases that effect is fairly small. However, really large changes in either PH or TA will change the other enough to notice. This is why I said that my procedure isn't perfect. Still it should end up close enough in all but the most extreme situations. If you really want to go through the ideal way to adjust things in every possible case it would run to a dozen pages.

    When TA is really high it takes more acid to lower the PH than it would when TA is lower. It isn't "difficult", you just need to have enough acid.

    After any really big change to PH or TA, run the pump for at least an hour and then test both PH and TA again before making any further changes. If you are only making small adjustments you can ignore this.
    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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    Diver's Avatar
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    Re: adjusting TA and PH - geenral approach

    i think you convinced me to not to worry about the generic approach at this point, but rather see where my balance is before i open the pool and then take it from there.
    26K In-ground Vinyl Pool | Hayward DE4820/SP0710XR50 filter | 1.125 HP Dual Speed Hayward Super Pump | Aquasol Solar

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