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Thread: Cause and remedy for the wall stain

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    Question Cause and remedy for the wall stain

    Hi just wonder how can I treat the pool wall stain, as shown in the attached picture. The stain cannot be brushed off. I have been running the cleaning robot 30min daily and brushing the wall weekly for a few weeks. Didn't get the condition improved.
    Highly appreciate if anyone could give an idea.

    Test levels today;
    FC 5.0
    CC ~0
    PH 7.8
    TA 110
    CYA ~80 (very subjective though with the TF100 kit)
    CH 700~800 (cannot replace water due to water restriction ...)

    photo link:
    Shared album - Eric Yang - Google Photos

    ---------------------------------------------------------------------------------------------------------------------
    20 year old 12k Gal IG pool with SPA, Concrete white plaster, 1.0HP pump, Cartrige filter

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    Mod Squad YippeeSkippy's Avatar
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    Re: Cause and remedy for the wall stain

    Ok, When you feel the stained area is it rough?? Your CH is high so scale is a definite possibility. With CH high we like to have you keep your pH on the lower end of normal range to help counteract the calcium. Try to go to 7.2-7.4.

    Other wise we ask you to perform some quick tests here- hold a chlorine puck up against the stain for a few minutes. Does it lighten it? If so that suggests its organics.

    Next- take a handful of cheap Vitamin C tablets and put them in a sock and bang it up to crush them up a bit. Now hold that sock full of Vitamin C against a different area of stain than where you held the chlorine puck. If it lightens it it suggests you have metals in the water.

    How are you sanitizing the pool? Do you ever use algaecides?

    Yip
    My Amazon Smile for November12K Fiberglass IG, Infinity 4000 automatic cover, SWCG, Hayward Sand Filter, Hayward 1.5 Pump, Doheny Discovery Robot, Savi Melody LED pool lights, outdoor speakers and other assorted doo-dads. Sundance Altamar Hot Tub.
    Our pool build--> Our Pool Solved Our Sloping Yard Skippy's Cheap Pool Cooler -->Skippy's New Fountain

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    Mod Squad pooldv's Avatar
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    Re: Cause and remedy for the wall stain

    The Vit C test will tell you if it is iron if it lightens the stain. Another test is to put dry acid in a sock and rub it on a stain. This will clear up a copper stain or calcium scale.

    I can't see a pic in your post. You can upload the pic to photobucket, copy the IMG code and paste it in your post. That will embed the pic in your thread so everyone can see it.
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    Re: Cause and remedy for the wall stain

    Quote Originally Posted by pooldv View Post
    The Vit C test will tell you if it is iron if it lightens the stain. Another test is to put dry acid in a sock and rub it on a stain. This will clear up a copper stain or calcium scale.

    I can't see a pic in your post. You can upload the pic to photobucket, copy the IMG code and paste it in your post. That will embed the pic in your thread so everyone can see it.

    Thanks for the advice. Can you see the pic now? I found it was too big to paste.
    pool_wall.jpg

    - - - Updated - - -


    Thanks I'll try. I never used any algaecides to sanitize the pool. In the past 4 months the water has been clear till now with TFPC.


    Quote Originally Posted by YippeeSkippy View Post
    Ok, When you feel the stained area is it rough?? Your CH is high so scale is a definite possibility. With CH high we like to have you keep your pH on the lower end of normal range to help counteract the calcium. Try to go to 7.2-7.4.

    Other wise we ask you to perform some quick tests here- hold a chlorine puck up against the stain for a few minutes. Does it lighten it? If so that suggests its organics.

    Next- take a handful of cheap Vitamin C tablets and put them in a sock and bang it up to crush them up a bit. Now hold that sock full of Vitamin C against a different area of stain than where you held the chlorine puck. If it lightens it it suggests you have metals in the water.


    Yip
    ---------------------------------------------------------------------------------------------------------------------
    20 year old 12k Gal IG pool with SPA, Concrete white plaster, 1.0HP pump, Cartrige filter

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    Re: Cause and remedy for the wall stain

    I would also mention that it looks like your FC is low for your CYA: Pool School - Chlorine / CYA Chart

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    Re: Cause and remedy for the wall stain

    Hi Marian

    Thanks for the note. The issue is that I really not sure how accurate of my CYA test. The TF100 test kit requires me to drop the combined liquid until "cannot see the black mark at the bottom of the CYA viewing cylindra". I cannot define to what extent is regarded "cannot see", as I was feeling the a dark spot was always there, though very blur...
    Anyways, I'll add more bleach as it should bring no harm.

    Quote Originally Posted by MarianParoo View Post
    I would also mention that it looks like your FC is low for your CYA: Pool School - Chlorine / CYA Chart
    ---------------------------------------------------------------------------------------------------------------------
    20 year old 12k Gal IG pool with SPA, Concrete white plaster, 1.0HP pump, Cartrige filter

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    Mod Squad pooldv's Avatar
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    Re: Cause and remedy for the wall stain

    Here is what the cya test looks like, https://www.taylortechnologies.com/C...P?ContentID=36

    Yes, I can see the pic now. Are the stains raised and rough?
    TFP Moderator
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    2012 build and pics, 20k gal gunite, black onyx pebblesheen, OK flagstone, IntellifoVS, cart filter w/Pleatco, IC40 SWG, Solartouch, 5 12'x4' solar panels, HP50HA heat pump, 8mil solar cover, borates, TF-100 test kit, SONOS, Doheny's Discovery Robot, hot tub on bleach

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