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Thread: High Chlorine Usage

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    High Chlorine Usage

    Hello All,

    I found this forum, pool school, and the pool calculator about two months ago when I couldn't get my pool algae free here in Las Vegas. I ended up ordering a TF-1000 test kit and found my CYA was > 200 (My usual way of adding chlorine was with dichlor, which Leslie's Pools totally supported!)

    Anyways, I partially drained the pool and started using liquid bleach. The pool cleaned up very quickly and has been wonderful ever since! The way you explain everything here and with pool school is great. I always hated going to the pool store and they would tell me to "shock every week" and I'd ask why and they'd say "because you need to!". I hate explanations like that!

    Anyways, onto my question. Since I have been using liquid bleach, I'm finding I have to use 5-6ppm per day to keep the chlorine level stable, which seems like quite a bit. My stats are currently:

    Size: 15,500 gallons
    FC: 5ppm
    CYA: 40
    PH: 7.8
    CH: ~650 (this is freshly filled water, we just have amazingly hard water)
    TA: 90

    I'm not using any type of solar cover or anything. I'm thinking 5-6ppm per day is quite a bit to be using? Any suggestions? I'm thinking I need to increase the CYA since I am in Vegas and we have tons of sun. Also, we rarely use the pool, maybe two of us every other week for a couple hours, so I don't think it is due to bather load.

    If I do want to increase the CYA, how high should I go? Also, I would likely use dichlor to increase CYA, if I do that, am I supposed to dose the dichlor and then wait a week or so before testing or how long do I need to wait before I can test for CYA and be confident that it isn't still increasing?

    Thanks for any input and this great site, it has already helped a lot!


  2. Back To Top    #2

    In the Industry

    duraleigh's Avatar
    Join Date
    Apr 2007
    Sebring, Florida

    Re: High Chlorine Usage

    Hi, Jeff,

    The first thing I would do is confirm that you have no overnite loss of chlorine.

    Test FC in the evening once the sun is off the pool. don't add anything, just test and record.

    Test FC again the next morning and compare your results from the night previous.

    If your FC has dropped 1.0ppm or more, you have algae in your pool and that is what is consuming your chlorine.
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

  3. Back To Top    #3
    critterdoc's Avatar
    Join Date
    Oct 2008
    30.0217 -090.2403

    Re: High Chlorine Usage

    Quote Originally Posted by duraleigh
    If your FC has dropped 1.0ppm or more, you have algae in your pool and that is what is consuming your chlorine.
    Other than the crummy plaster in our pool, the water has never looked as good as it does since I drained a significant percentage of water and began practicing BBB! There are several dozen deep erosions in the plaster ranging between 1/4 and 1 square inch in area. Some of these defects are deep, appearing to penetrate the entire thickness of the plaster at their deepest points. One half or more of these erosions contain a sprinkling of black material at their deepest points - presumably black algea. This has been a persistent problem since the plaster took a hit during and immediately after Katrina. I've not seen even a hint of green or yellow since I began BBB. I've brushed the buggers daily with a stainless steel brush to the best of my ability but to do it well I would have to get wet which ain't gonna happen, and over the last week and a half I've jugged the beejebies out of the pool with 6% bleach. Thus far I'm adding between and and two qts per day to hold FC above 7 with CYA at 40-45. So, here's my questions:

    1) Can what appears to be to be relatively small sized and patchy colonies of BA reduce FC significantly over several days.

    2) Does addition of N-Alkyl Dimethyl Benzyl Ammonium Chloride or it's equivalent make any sense if continued use of bleach does not show improvement within another week or so. What is the practical downside to using these kinds of algaecides? I'm anticipating that the cure will be to replaster but it might be the better part of a year before we can make that move.

    3) Does anyone know of a garden-hose powered rotary scrub tool that offers a stainless steel brush bristle option?
    20K gal gunite, plaster in poor condition post Katrina
    1.0 or 1.5 hp primary pump
    Polaris 280 and Polaris pump
    Her name is: Free To Good Home :wave:

  4. Back To Top    #4
    spishex's Avatar
    Join Date
    Oct 2008
    Hillsborough, NC

    Re: High Chlorine Usage

    The downside of that algicide is foaming. It is a surfactant, like soap, which reduces the surface tension of water and allows it to more easily penetrate and kill things. How much have you added?

    Black algae are most common in spots with bad water circulation, like pits in plaster, so you're right. That's your permanent solution. But you can kill it with chlorine, just much more than you've been using. The chem docs will be along shortly with your prescription.

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