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Thread: Disappearing chemicals?

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    Disappearing chemicals?

    Today I was told about a pool that one of my coworkers takes care of. Every week the pool is low on salt. The pool has an automatic filler, so we have been working under the assumption that it is probably losing water, and the autofill keeps it topped off. Today the pool was low on salt again. It had dropped by about 200 ppm since last week. When the tech tested the CYA, he found that the CYA had not dropped. So how could it be possible to lose 200 ppm salt, but not see a change in the CYA?
    TreeFiter

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    Saugerties, NY

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    Re: Disappearing chemicals?

    Is the pool using stabilized chlorine in some form that may be keeping the CYA up, but obviously not the salt? Is the pool,owner throwing tabs in the skimmer or shocking with dichlor that you guy is not adding?
    TFP Moderator 39 X 18 23,000(ish) freeform gunite; built 2007ish; Pentair Triton II TR100 600lb Sand filter; 2 HP Pentair pump with 2.2 HP AO Smith single speed motor; 2 skimmers, 1 main drain, 4 returns w/waterfall, Stenner 45MHP2 3GPD running@ 60% - 15 gal Tank; heated by the sun CYA 200+ when I started - 50 now. Dolphin Supreme M5 Pool Cleaner. Hot Springs SX Spa, 285 gallon

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    Re: Disappearing chemicals?

    Quote Originally Posted by tim5055 View Post
    Is the pool using stabilized chlorine in some form that may be keeping the CYA up, but obviously not the salt? Is the pool,owner throwing tabs in the skimmer or shocking with dichlor that you guy is not adding?
    Not likely. Its a relatively new pool, and has had a SWG from the start. Whenever there has been any issue in the past, this customer would call the tech for guidance. I really doubt she is adding anything to the pool without talking to him about it first.
    TreeFiter

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    Re: Disappearing chemicals?

    200 ppm is within the error of the salt test. We don't know if it lost any or not.
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
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    Re: Disappearing chemicals?

    Quote Originally Posted by duraleigh View Post
    200 ppm is within the error of the salt test. We don't know if it lost any or not.
    Its low every week despite adding salt over and over again. Its usually around 2500-2600ppm. If it were the margin of error of the test being used, I would think that after adding salt week after week, the test would start to register well above this.
    TreeFiter

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    Saugerties, NY

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    Re: Disappearing chemicals?

    How about the CH, is that dropping too? Of course, if the CH is low because it's not a plaster pool then a drop in CH can be hard to detect.
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    Re: Disappearing chemicals?

    Regardless, you cannot take a 200 ppm loss from one week to the next and call that a loss. If at the end of four weeks, you are down 800 ppm then that is a loss that's actionable.

    If you replenish 200 ppm every week and it never rises, that's actionable, too. There is no answer for that however as you have ruled out replacemant water.
    Dave S.
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    Re: Disappearing chemicals?

    Quote Originally Posted by chem geek View Post
    How about the CH, is that dropping too? Of course, if the CH is low because it's not a plaster pool then a drop in CH can be hard to detect.
    I don't have any information regarding the CH, but I'm not sure I would put much confidence in it either way since the autofill is using well water. Whatever CH is in the pool may have come from the well in the first place. Might be worth looking at it, but I'm not sure I would put too much confidence in it.
    TreeFiter

    Pool Technician
    Saugerties, NY

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