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Thread: Burn looking marks on Fiberglass

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    Join Date
    Apr 2013
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    Suburbs of Chicago
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    Burn looking marks on Fiberglass

    Hello All,

    Just finished my Pool Opening SLAM and the pool looks great for the most part. There are a couple of black marks on the fiberglass that almost look like burns. Since I am about to do a AA treatment I took a little AA and rubbed it on one of the marks and after a little elbow grease it fades away. I wasn't doing the AA for these marks just a couple of others, but hey if these get lifted to then great! I have a couple of these around the top half of the pool (on the fiberglass) and usually right in the center of a welt. A welt as in a bubble like shape forming on the 30 Yr old fiberglass. Any ideas as to what is happening? Seems like there are more then last year.

    Last Night Test Results
    FC: 12
    PH: 7.5
    CH: 220
    TA: 80
    CYA: 30

    Here are a few pictures.

    On steps



    On steps



    Overall



    Thanks
    Fiberglass/Concrete IG
    Pool Size: 16500 gallons
    Filter: Hayward S244T Pro Series Top-Mount Sand Filter
    Pump: Hayward 1 HP Super Pump

  2. Back To Top    #2
    Casey's Avatar
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    Apr 2007
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    SW PA
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    Re: Burn looking marks on Fiberglass

    Nice pool BNighGrow! I would say those are metals and the AA should get rid of it.

    I can't help with the welt that you speak of and don't know what would cause it.

    Are you done SLAM'ing the pool?
    I'd bet you my bikini you'll never get TFP water from a pool store!

    24' Sharkline Venture De Filter

  3. Back To Top    #3

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    Re: Burn looking marks on Fiberglass

    Hey thanks! Ya slamming is complete and I'm letting the FC fall in preparation for AA. I was just mentioning that the marks were showing up specifically on the welts and I think its just due to the old age. I believe AA will get rid of them. Thanks

    Fiberglass/Concrete IG
    Pool Size: 16500 gallons
    Filter: Hayward S244T Pro Series Top-Mount Sand Filter
    Pump: Hayward 1 HP Super Pump

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    Casey's Avatar
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    Apr 2007
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    Re: Burn looking marks on Fiberglass

    Keep us updated.
    I'd bet you my bikini you'll never get TFP water from a pool store!

    24' Sharkline Venture De Filter

  5. Back To Top    #5

    In the Industry

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    Re: Burn looking marks on Fiberglass

    The welt is probably the layers of fiberglass delaminating over time as moisture has penetrated it from the backside
    Over 30 years in the pool business
    We build vinyl, fiberglass, stainless steel pools
    Certified in Hydraulics

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    Butterfly's Avatar
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    May 2007
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    Re: Burn looking marks on Fiberglass

    I wasn't doing the AA for these marks just a couple of others, but hey if these get lifted to then great!
    If you only have a few more stains, maybe just put some AA in a sock and move it around on the stains. This would be lots easier than the complete AA treatment.
    TFP Moderator TF100 Test Kit TF100 TestKit YouTube Channel PoolMath
    You're done SLAMing when:
    1)You lose 1ppm or less FC overnight, & 2)You have .5ppm CC's or less, & 3)your water is clear.

    ~ One should not use a sledge hammer to swat a mosquito. ~

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  7. Back To Top    #7

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    Apr 2013
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    Suburbs of Chicago
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    Re: Burn looking marks on Fiberglass

    Ya I have a few of those spots but then I have a lot of another stain. But I'll keep your idea for future spot checking.

    Fiberglass/Concrete IG
    Pool Size: 16500 gallons
    Filter: Hayward S244T Pro Series Top-Mount Sand Filter
    Pump: Hayward 1 HP Super Pump

  8. Back To Top    #8
    brysclar's Avatar
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    May 2015
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    Tampa, FL
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    23

    Re: Burn looking marks on Fiberglass

    Hey there, thanks for this post. I have the same exact situation (dark stains on top of bubbles). Did you find a solution?
    10K Gal IG Freeform Fiberglass Pool
    1.5 HP Centurion Pump
    Pentair CC100 Cartridge Filter
    Hayward Automatic Pool Cleaner (model unkown)

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