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Thread: Chlorine only test cylinder

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    mitch08's Avatar
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    Jun 2008
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    Chlorine only test cylinder

    Is there any reason why after a year my chlorine only test cylinder would become very black?
    It seems to have a residue on there that won't come off.

    I just purchased a new one, but Im wondering if its the same reason that I get dark lines on any plastic or fiber glass at water level?

    No big deal... It comes off easy enough, but it appears relatively quickly. I scrubbed it off yesterday and it was back this morning after a heavy rain...
    18x38 Inground Liner (25k gal) Paver surround, multi-speed pump, DE Filter, Raised spill over spa, TF-100

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    Mod Squad Bama Rambler's Avatar
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    Re: Chlorine only test cylinder

    That's why there is a "chlorine only" vial. You can clear it up by bleaching the vial. It's caused by the DPD reagents.

    The ring around your pool has nothing to do with the black around your vial. Get a scum ball and throw it in the skimmer, then clean the pool with Magic Erasers.
    Dave J. TFP Moderator
    24' x 52" Round AGP. 2hp/¼hp SPL Power-Flo 2-speed pump. 200sqft Waterway Cartridge Filter. 45MHP2(3GPD) Stenner Peristaltic Pump
    Pool School ----- Pool Math ----- TF-Test Kit

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    mitch08's Avatar
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    Re: Chlorine only test cylinder

    Awesome thanks!!!
    18x38 Inground Liner (25k gal) Paver surround, multi-speed pump, DE Filter, Raised spill over spa, TF-100

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