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Thread: Need help with chlorine/algae after iron stain treatment.

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    Join Date
    Jul 2015
    Location
    Houston, TX
    Posts
    41

    Need help with chlorine/algae after iron stain treatment.

    Performed ascorbic acid treatment for iron stains followed by the addition of Stain-Treat sequestrant one week ago today. Struggling unsuccessfully to keep chlorine up to min of 5 needed based on my CYA level due to treatment. Now have mustard algae from pool having zero chlorine for so long. Was told not to shock for two weeks after AA treatment. Just added calcium hardness increaser today. Chlorine is back to zero.

    Three questions:
    1) How long do I need to wait after adding the calcium hardness increaser before I can add any chlorine.
    2) How long does the AA treatment continue to eat up the chlorine?
    3) When can I shock to get rid of mustard algae after ascorbic acid/sequestrant treatment.

    pH = 7.4
    FC = 0 (have been adding tons of 10% liquid chlorine for past several days - get it up to 5 for a few hours then it drops again)
    CC = 0
    TA = 70
    CH = 240 (was 150 this morning before I added the calcium chloride - slowly trying to get it up to at least 300. Today was first addition of calcium)
    CYA - 80


    IG, 20k gallons, new plaster 2014
    Hayward DE model 4820 filter, Hayward Super II pump, Pentair Chlorinator #320 - all new in 2014
    Kreepy Krauly cleaner, one skimmer, single floor drain, city water, Taylor K-2006 test kit

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    duraleigh's Avatar
    Join Date
    Apr 2007
    Location
    Sebring, Florida
    Posts
    30,077

    Re: Need help with chlorine/algae after iron stain treatment.

    Regardless of how much it takes, you should never allow your FC to drop to zero.

    Your CYA is wa-a-ay too high for manual chlorination. It looks like you have used tabs (pucks).....that's how it got too high.

    Your sig also indicates you used city water to fill and as your refill yet you report iron stains.......that's fairly unusual for city water.

    So, you have several problems to deal with.

    It seems like you have algae (whether or not you can see it, and it appears your CYA needs to be cut in half and it appears your water is iron laden.

    If it was my pool I would....

    1. Test your fill water for iron. If your city water is truly a source for iron, I would consider trucking in water. Iron in your water is a continual monster.

    2. Drain 50% of your pool and fill with iron free water.....don't just drain "a lot"....drain 50% and your CYA will drop to 40 ppm.

    3. Now that your CYA is down and you have the iron under control, it is time to SLAM your pool. Do so according to the exact directions in Pool School.

    4. Stop using pucks.

    Sorry to bear such troublesome news but I can think of no other way to get your pool manageable
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

  3. Back To Top    #3

    Join Date
    Jul 2015
    Location
    Houston, TX
    Posts
    41

    Re: Need help with chlorine/algae after iron stain treatment.

    Duraleigh,
    The pool and pipes are 28 years old. My CYA was above 100. I did a 60% drain and refill before starting the treatment. I'm assuming since it took two years for the iron stains to show up that the source may be in the older pipes. I got my CYA down to 65 after the refill but now it's reading 80 (likely didn't go up but rather got read wrong in bad lighting). I have NOT used ANY pucks or granular shock since the refill and was only using the inline chlorinator on the lowest setting as a small backup to the primary liquid chlorine. Turned inline off completely before refill and it will remain completely off forever.

    Either the ascorbic acid or sequestrant was supposedly the culprit in keeping my chlorine levels down at the acid treatment. I have been adding at least 1 1/2 gallons of 10% chlorine for the past several days as I read somewhere on here to bring the chlorine level up slowly after the stain treatment and not to shock for two weeks.

    So it's okay to go ahead and SLAM the pool only a week after the ascorbic acid and sequestrant and the same day as adding calcium increaser?
    IG, 20k gallons, new plaster 2014
    Hayward DE model 4820 filter, Hayward Super II pump, Pentair Chlorinator #320 - all new in 2014
    Kreepy Krauly cleaner, one skimmer, single floor drain, city water, Taylor K-2006 test kit

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