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Thread: Huge Acid Demand - Help Please

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    Join Date
    Jul 2007
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    South Florida
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    Huge Acid Demand - Help Please

    So a little background. Pool is around 20 yrs old, current diamond brite around 12 years. This past 'winter' I kind of let the pool go and it had algae on/off most of the winter. Had some trouble cleaning it up as even after I shocked it algae would seem to come back pretty quick. Also it was looking a bit dingy. So... I decided to drain, acid wash and refill (2nd acid wash). Got it all filled and balanced and pool looks fantastic but now I have this huge acid demand. Pool never drank so much in the past, maybe a cup or two a week. Now EVERY DAY I get 2-4 drops (roughly 2-4 need cups) needed on acid demand test (I use a K-2006). Pool is roughly 11k gallon SWG w/Autopilot in South Fla (under screen).

    Here are my current #s:
    pH - Keep putting it down to 7.5 ish but it jumps up to > 8 daily
    FC - 4, CC - 0
    TA - 80
    CYA - ~70ish
    Cal - 240
    Salt ~ 3400 ppm
    Temp ~ 86

    I understand that new plaster could affect pH rise/acid demand but this is > 10 years old and never had the problem, even after first acid wash. No additional added water except some rain since refill ~ 2 weeks ago. The pool sucking acid faster than a jet sucking fuel is driving me nuts.

    Any ideas on what is going on and how I can get acid demand back to like a cup or two a week like it used to be?
    Roughly 15x30 IG Gunite/Diamondbrite, 14,000 gallon
    Heliocol Solar 7(4x10) panels w/Aqua Solar controller, Intelliflo 4x160 pump, Hayward C1200 filter, Autopilot DIG-220 w/SC48 SWG, The Pool Cleaner sweep

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    JasonLion's Avatar
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    Re: Huge Acid Demand - Help Please

    In some cases an acid wash will expose a deeper layer of plaster that has not yet fully cured, giving a fresh plaster kind of effect on the PH (rapid rise for about a month, and slower for up to a year). However, I have never heard of that happening on a pool as old as yours. Plaster deeper down does cure eventually, and 12 years should be more than enough for it to cure all the way through.

    In any case it is worth lowering TA to around 60, or letting it get there on it's own. That will help a little, though perhaps not all that much.
    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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    laceygirl's Avatar
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    Re: Huge Acid Demand - Help Please

    Would borates help to stop the fluctuation of the pH?
    Intex Rectangle 18 x 9 x 52', 4544 gallon (18000 litres), 0.75 hp pool pump, 100 sqft Zodiac Titan Cartridge Filter - 40mm, Stenner Peristaltic Pump chlorine injection system, Intex Over The Wall Skimmer, Intex Fittings with 40mm plumbing Lil Patch Of Heaven. Build/Construction http://www.troublefreepool.com/threa...lice-of-heaven

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    JasonLion's Avatar
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    Re: Huge Acid Demand - Help Please

    Adding borates will slow down the PH increase significantly, but it won't stop it, and it won't change the total amount of acid needed.
    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: Huge Acid Demand - Help Please

    So this continues to frustrate me. I get the TA down to 60 or just below but it goes back to 70 or more in just a few days. I have to add around 2 cups DAILY just to keep it in normal range and more like 3 or more cups daily to keep the TA down. I'm going through jugs of acid way too fast (and too costly) and the thing that is puzzling me is this pool NEVER did this before, not after it was diamond brite'd and not after first acid wash. There just has to be something going on or something I can do to normalize this and get it back to the 1-2 cups per week it used to be. At this point I'm ready to fill it with concrete and it has never frustrated me that much in 20 years. Is there nothing else I can do, I just don't believe this isn't fixable.
    Roughly 15x30 IG Gunite/Diamondbrite, 14,000 gallon
    Heliocol Solar 7(4x10) panels w/Aqua Solar controller, Intelliflo 4x160 pump, Hayward C1200 filter, Autopilot DIG-220 w/SC48 SWG, The Pool Cleaner sweep

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    JasonLion's Avatar
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    Re: Huge Acid Demand - Help Please

    There are very few things that can raise TA. One is acid etching the plaster, which raises PH, TA, and CH. Another is things which increase the PH, like baking soda, soda ash, borax, lye, etc. And the final one is plaster curing.

    How old is your PH test reagent? Also, any chance the FC level has been above 10 this whole time? (I am starting to think about some really uniquely possibilities.)
    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: Huge Acid Demand - Help Please

    Plaster should be cured, none of the other things ever added but yea, was acid washed with a 50% solution. I don't think FC was ever > 10 except maybe right after fill before I added stabilizer and balanced everything out. It's been running around 1.5-5 (while I dial in the SWG). My reagent is around 18 months old, stored indoors in the a/c in its dark container.
    Roughly 15x30 IG Gunite/Diamondbrite, 14,000 gallon
    Heliocol Solar 7(4x10) panels w/Aqua Solar controller, Intelliflo 4x160 pump, Hayward C1200 filter, Autopilot DIG-220 w/SC48 SWG, The Pool Cleaner sweep

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