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Thread: lower TA with MA

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    Whidster's Avatar
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    lower TA with MA

    I just chatted with the pool guy that seems to be in sync with this site. I was looking for a fountain to aerate. He made the following suggestion and I wanted your opinion:

    Turn off system.
    Add 8 gallons of MA
    Wait 24-48 hours while TA outgasses
    Test TA -- should be near 0
    Add EZ PH (sodium hydroxide) (40 bags) to bring PH back up

    He says this is the fastest way.

    I have gotten my TA down from 250 to 220 by MA/Aeration method. Would his way be safe and quicker?
    20,000 Gallon Vinyl Splash AG pool. Goldline SWG. Two sand filters w. 1.5HP Sgl Spd pumps. Lexan Aqua Shield dome. Solar heating, with propane back-up.
    Camas, WA

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    JasonLion's Avatar
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    Re: lower TA with MA

    That is a terrible idea. 8 gallons of muriatic acid would drop your TA to zero right away, which is something of an over correction. It would also lower the PH so far that there would be damage to the vinyl liner, and most heaters, not good at all. No need to wait 24-48 hours, that will just make the damage from the low PH worse.

    Also, sodium hydroxide is caustic soda, which has caustic in it's name for a good reason, it is not very safe to handle (well, only a bit worse than muriatic acid).
    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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    Mod Squad JohnT's Avatar
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    Re: lower TA with MA

    Quote Originally Posted by Whidster
    I just chatted with the pool guy that seems to be in sync with this site. I was looking for a fountain to aerate. He made the following suggestion and I wanted your opinion:

    Turn off system.
    Add 8 gallons of MA
    Wait 24-48 hours while TA outgasses
    Test TA -- should be near 0
    Add EZ PH (sodium hydroxide) (40 bags) to bring PH back up

    He says this is the fastest way.

    I have gotten my TA down from 250 to 220 by MA/Aeration method. Would his way be safe and quicker?

    That's a fast way to damage your pool and will have very little effect on the TA level in the long term. The MA will sink to the bottom and stay there until you turn the pump back on. It's a very bad idea and won't work. Check out the pictures in this document http://z6.invisionfree.com/San4um/in...st&id=14034925 showing a dyed muriatic acid addition to a pool with no circulation.
    TFP Moderator
    20K Gallon 20X36 Vinyl Inground
    Hayward S244T Sand Filter with 1HP Whisperflo Pump. Liquidator C-201 and Solar Heat

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    Whidster's Avatar
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    Re: lower TA with MA

    Glad I asked! I am going with your instructions, but thought I'd run it by you.

    Once I get my FC down is there any reason not to swim with the TA high?
    20,000 Gallon Vinyl Splash AG pool. Goldline SWG. Two sand filters w. 1.5HP Sgl Spd pumps. Lexan Aqua Shield dome. Solar heating, with propane back-up.
    Camas, WA

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    JasonLion's Avatar
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    Re: lower TA with MA

    TA doesn't directly affect swimming. As long as PH and FC are good you can swim.
    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: lower TA with MA

    Never let your TA get that low, as the others have stated. If your TA is 220 right now, in a 20k gallon pool, it should only take 2-3 gallons of MA to lower those numbers down. But keep an eye on the PH as you lower your TA.

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    Re: lower TA with MA

    Every gallon of full-strength Muriatic Acid (31.45% Hydrochloric Acid) in 20,000 gallons of your pool water will lower the Total Alkalinity (TA) by 25 ppm no matter how it is added. So as others said, he is adding way too much too quickly. 8 gallons would wipe out 200 ppm TA and the pH would plummet. If your starting TA were <200 ppm TA, then the pH would plummet below 4.5, but it's actually much worse because he would have you add the acid with no circulation so it would locally get to very low pH as others have stated even though your overall TA is >200. It does seem he calculated to try and not completely wipe out the TA, but the pooling of acid without the circulation is a big risk to damaging the liner.

    At least he realized that raising the pH with sodium hydroxide would not increase carbonates the way that pH Up (sodium carbonate) would do.
    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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