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Thread: Yellow/Brown dusty deposits that reappear repeatedly

  1. #31
    mbar's Avatar
    mbar is offline Lifetime Member Whizbang Spinner mbar 3 stars mbar 3 stars mbar 3 stars mbar 3 stars
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    Default Re: Brown deposits on pool bottom

    I think what you have put in your pool "super green" algaecide is an aglaecide that has copper in it. This being said, you may have a problem when you raise your chlorine to shock levels, as you may get some staining due to the copper in the algaecide which I read is 7%. Hopefully the algaecide has a sequesterer in it that keeps the copper in suspension. It really is not a good idea to introduce any metals in the water. High chlorine levels will kill any algae, you just have to keep it high enough long enough for it to do the job. With a cya of 40 you need to take your chlorine levels up to 15ppms and keep it there being very consistant. Everytime it falls below 15ppms, you have to add enough chlorine to take it back to 15. If you read through this thread, you will see this algae sometimes needs even higher levels of chlorine to kill it. I would suggest that you take your chlorine up to 15 - 20ppms and keep there, brushing and backwashing as needed. Be very consistant!!! You may want to drop your ph down to 7.2 while you are shocking the pool to help keep staining away. If you are consistant with the high chlorine levels, and keep your filter running 24/7, you should be able to get rid of this once and for all
    Northeast PA
    16'x32' kidney 16K gal IG fiberglass pool; Bleach; Hayward 200lb sand filter; Hayward pump; 24hrs; Pf200; well; summer: none; winter: mesh; ; PF:7.5

  2. #32
    chem geek is offline PF Supporter Whibble Konker chem geek 4 stars chem geek 4 stars chem geek 4 stars chem geek 4 stars
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    Default Re: Brown deposits on pool bottom

    I've been doing some thinking and looking at the numbers for this hard-to-kill yellow/mustard algae. Though it appeared that high chlorine levels were needed to kill this algae, my saying that it was around 1.0 ppm disinfecting chlorine (HOCl) assumed that the pH was around 7.5. Normally, the CYA acts as a chlorine buffer so higher pH doesn't change this concentration by that much, but this buffering starts to fall apart at the higher HOCl concentrations needed to kill this algae. What this means is that perhaps the actual disinfecting chlorine concentration needed to kill yellow/mustard algae is not 1.0 but is less, perhaps 0.7, but adding a lot of chlorine makes the pH rise which results in less disinfecting chlorine than I was assuming.

    For practical purposes, using this chart when you start at around a pH of 7.5 and then add chlorine it is probably OK if you use the 0.3 ppm column (or at least 0.2) for green algae and the 1.0 column for yellow/mustard algae. However, next time this happens to someone, we should try to not only add chlorine to raise FC, but also start out at a lower pH (perhaps 7.2 or even 7.0) or add acid to keep the pH lower since that will allow for lower FC levels to kill the algae (meaning less bottles of chlorine and therefore lower cost).

    I suppose this will have to wait until next August to see... Of course, everyone will probably be adding PolyQuat 60 and/or have 50 ppm borates in their pool and no one will get yellow/mustard algae so we can "experiment".

    Richard
    Last edited by chem geek; 10-05-2006 at 07:33 PM.

  3. #33
    matt4x4 is offline Lifetime Member Verb Herder matt4x4 2 stars matt4x4 2 stars
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    Default Re: Brown deposits on pool bottom

    Can SOMEONE PLEASE STICKY this post, it contains very usedful information to a problem that seems to be reocurring frequently!
    Also, if the title can be changed to "Yellow/Brown dusty deposits that reappear repeatedly" it may help.

    Oh yeah, can it be cross stickied to the ALGAE forum too (because that just makes sense to me) ???? and maybe rated as 5/5 since it's helped many get rid of this crap through persistence even beyond the pool looking sparkling clean...
    Last edited by matt4x4; 05-04-2007 at 10:08 AM.

  4. #34
    Watermom's Avatar
    Watermom is offline SuperMod Emeritus Quark Inspector Watermom 4 stars Watermom 4 stars Watermom 4 stars Watermom 4 stars Watermom 4 stars Watermom 4 stars
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    Default Re: Brown deposits on pool bottom

    OK, Matt. I've done as requested. I am going to lock this particular thread, however, so we don't get people responding to both threads. If anyone wants to add any posts to this thread, please do so in the algae forum.

    Thanks.

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