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Thread: Black waterline staining, doesn't seem to be "scum"

  1. Back To Top    #1

    Join Date
    Jun 2015
    Location
    Grafton, MA
    Posts
    5

    Cool Black waterline staining, doesn't seem to be "scum"

    Hi, we have a pretty old vinyl liner pool, ~ 27,000 gallons. We use Bromine tablets in a cylinder-type dispenser near the pump. During the last few years, I've noticed that the inside of the white plastic skimmer has begun to develop a pretty ugly black stain which seems to have formed at the waterline. Now I've read quite a few posts here talking about black stains inside the skimmer, but they all talk about "scum" and are described as being gooey or sticky or gummy, and having to do with oils in the water.

    But our staining isn't like this - it's quite "dry" in the sense that it seems to be embedded into the plastic itself. If you run a finger (um, I guess not just any finger; specifically one of your own ) over the stain you don't feel any gumminess or stickiness. In fact you cannot feel it at all.

    I'm guessing that since our staining is different from the descriptions of black staining that I've read about here, it may have some other cause, and wondering how it might be remedied. IMO it makes the inside of the skimmer look pretty disgusting.

    If it's of any relevance, the few inches of our liner that is always above the waterline also have a darkness/blackness coloration. I tried using a magic eraser to lighten that up to match the color of the liner that's always underwater, but using that seemed to be rubbing the design out of the vinyl, which looked even worse.

    Thanks for any suggestions!

  2. Back To Top    #2

    Join Date
    Jun 2015
    Location
    Raleigh
    Posts
    357

    Re: Black waterline staining, doesn't seem to be "scum"

    Well since noone else has chimed in....It's either algae, scum or metals....Put a Vitamin C tablet on the stain and see if it has any affect. Then do the same with a chlorine tablet. If neither of those has any effect, then use a magic eraser in the skimmer to clean it, and throw a scum ball in there.
    18' x 38' Pool, 3' to 8' Depth
    Vinyl Liner
    SWG
    Variable Speed Pump
    Sand Filter

  3. Back To Top    #3

    Join Date
    Jun 2015
    Location
    Grafton, MA
    Posts
    5

    Re: Black waterline staining, doesn't seem to be "scum"

    Will try your suggestions. Thank you for taking the time to reply. FWIW I did try to find similar posts here but couldn't. Thanks again.

  4. Back To Top    #4
    Desert Oasis's Avatar
    Join Date
    Feb 2016
    Location
    Tucson,Az
    Posts
    8

    Re: Black waterline staining, doesn't seem to be "scum"

    I noticed a black scum in one corner of the pool as well, when I rubbed it with my finger it was slimy like grease, I sprayed a little simple green on a towel and wiped it off. Wonder if it was from using pool lube on all o-rings ?
    16,000 Gallons in ground plaster with water fall using skimmer and Hayward pool vac Pentair CCP320 filter.

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