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Thread: 1st timer...will iron re-absorb as fc. Ph, alk. Decrease?

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    Join Date
    Jul 2012
    Location
    Charleston, SC
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    1st timer...will iron re-absorb as fc. Ph, alk. Decrease?

    I boosted the swg which took chlorine from 0.4 to 10. The water turned brown due to iron being oxidized out of the water I'm told. Will the iron re-absorb into the water as my FC, PH, and Alk come down to good levels? Or do I have to sequester?
    The test before boost was
    CYA 0
    FC 0.4
    PH 8.7
    Alk 285
    Salt 3500
    Then after boost and adding chemicals from pool store it was
    CYA 10
    FC 10.0
    Ph 8.1
    Alk 225
    Salt 3600
    I added 1.75 lb stabilizer. 2 bags burn out, 9 oz banish and I'm adding 1.25 lbs Lo N Slo per day for last 3 days. if I keep adding lo n Slo should the FC, ph, and alk get to a normal level? And how long should that take?
    5400 gal
    cartridge filter
    easy set 18' x 48" AG round inflated ring
    1/2 hp pump 1500 gph with SWG
    installed 7/9/12

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    JasonLion's Avatar
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    May 2007
    Location
    Silver Spring, MD
    Posts
    37,879

    Re: 1st timer...will iron re-absorb as fc. Ph, alk. Decrease

    Welcome to TFP!

    Yes, as the levels come down the iron will re-dissolve. If you are lucky some of it will get filtered out while it is coloring the water.

    FC will come down fairly quickly as soon as the sun is on the pool tomorrow. Lowering PH is mostly a question of adding the correct amount of acid (Lo-n-Slow will do, but muriatic acid is less expensive). Alkalinity (TA) takes time to lower, see the complete instructions at Pool School.
    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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    Join Date
    Jul 2012
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    Charleston, SC
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    Re: 1st timer...will iron re-absorb as fc. Ph, alk. Decrease

    Thanks for the welcome and your response!
    The pool calculator says to add 18 oz of 31.45% Muriatic acid to lower Ph .79 which will put me at 7.3, should this happen within 24 hours or should I do this daily until I reach my target number?
    Any guess as to how much time (days) it will take to lower my TA from 225 to a normal range (100 or so?) if I lower the Ph (from 8.1 to 7.3) by adding the 1.25 lbs/day of Lo n slo from BIoguard...or should I switch to muriatic acid?
    I am filtering the iron out with cotton tshirts in the skimmer basket and they're collecting some but my filter is only grabbing small amounts of sand sized granules...I can barely see the bottom (48") and it is not stained...it looks like all the iron is suspended in the water.
    5400 gal
    cartridge filter
    easy set 18' x 48" AG round inflated ring
    1/2 hp pump 1500 gph with SWG
    installed 7/9/12

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    JasonLion's Avatar
    Join Date
    May 2007
    Location
    Silver Spring, MD
    Posts
    37,879

    Re: 1st timer...will iron re-absorb as fc. Ph, alk. Decrease

    For large PH changes it is best to add about half the amount calculated, give it half an hour to an hour to mix in, test the PH and continue adjusting from there. The calculations for quantities when making PH changes are never exactly right. Continue this cycle as frequently as practical until your PH is down around 7.2 to 7.4.

    You can whatever Lo-n-Slo you have, but longer term I recommend using muriatic acid instead, though mostly that is because it is must less expensive.

    Lowering TA will take a while. You will make a lot of progress just at first, but then the process will slow down and take awhile. After you have made the initial PH adjustment down to 7.2-7.4, you can make subsequent PH adjustments about once every day or two, depending on how quickly your PH rises.
    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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    Join Date
    Jul 2012
    Location
    Charleston, SC
    Posts
    3

    Re: 1st timer...will iron re-absorb as fc. Ph, alk. Decrease

    Thanks. When you say to continue the cycle to lower the ph as often as practical, does that mean I can keep adding dry acid (then muriatic acid when the dry acid runs out) on an hourly basis until I reach my target ph?
    5400 gal
    cartridge filter
    easy set 18' x 48" AG round inflated ring
    1/2 hp pump 1500 gph with SWG
    installed 7/9/12

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