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Thread: Yellow stains on fiberglass

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    Yellow stains on fiberglass

    Hi all, Not sure if this is the right place to post this topic, but does anyone know why we are getting yellow stains on our white fiberglass pool? I've tried to brush it off, but that is not working. What is the cause and how do I remove these stains? Many thanks!
    10k gallon fiberglass freeform pool, Paramount SwingJet system, Dolphin DX5 robot, Pentair 48" Tagelus sand filter with glass media, WhisperFlo 1 HP pump, Hayward H200FDN natural gas heater, TF-100 Test Kit, and, of course, Margaritaville Tahiti blender!

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    BoDarville's Avatar
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    Re: Yellow stains on fiberglass

    Our pool occasionally gets similar staining from some sort of plant/pollen that occasionally gets blown in on windy days. While it does not brush out immediately, it goes away on its own usually on that same day.

    In your case, it could range anywhere from that to metal stains to (hopefully not) mustard algae. One quick way to determine if it is metal vs. organic in nature is to take a Vitamin C tablet and rub that on a part of the stain. If it goes away, then it's metal. If you do not have a Vitamin C tablet then you could approach it from the other angle...try rubbing a trichlor puck on the stain. If it fades, then the stain is organic and not metal.

    Of course, posting a full set of test results will allow us to help you better by giving us a bit more insight as to what's going on.
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    Re: Yellow stains on fiberglass

    hi. thanks for the reply. we have had a LOT of pollen and things blowing in from the trees lately, but the stains are not rubbing off. a vitamin c tablet, like a supplement pill? (sorry, pool newbie here!). re: metals, we did just add a few inches of water from the garden hose to bring the level up, and we have hard water locally. had planned to use Pool Magnet Plus after adding that, as the local pool store recommended it whenever adding water from the garden hose. is it possible that could remove it (if it's from metals)? i am taking a water sample to the pool store later this week to run full diagnostics, so i can reply back with accurate numbers at that point.
    10k gallon fiberglass freeform pool, Paramount SwingJet system, Dolphin DX5 robot, Pentair 48" Tagelus sand filter with glass media, WhisperFlo 1 HP pump, Hayward H200FDN natural gas heater, TF-100 Test Kit, and, of course, Margaritaville Tahiti blender!

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    BoDarville's Avatar
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    Re: Yellow stains on fiberglass

    Quote Originally Posted by DOMO
    a vitamin c tablet, like a supplement pill?
    Yes, exactly. Vitamin C contains ascorbic acid and will remove metal stains. If the stains are indeed metal, you can purchase a larger quantity of ascorbic acid to remove the stains. Here's a bit more information on dealing with metal stains: Metals in the Water and Metal Stains

    BTW, if the Vitamin C is in an enclosed capsule, you will have to break/crush the capsule so that the raw Vitamin C gets in direct contact with the stain.
    Gold Supporter, TFP Lifetime Supporter, 26,680 gal Plaster IGP 3.5 - 10' depth / Attached Waterfall Spa, Manually Chlorinated, Triton Sand Filter, 1.5 HP * 1.1 SF = 1.65 SFHP 1-speed Pentair WhisperFlo WF-26 Pump, 400K BTU NG Teledyne Laars Series One Heater, Polaris 360, Test Kit Comparison, Chlorine/CYA Chart, SLAMing Your Pool, OCLT
    A good test kit is an investment, not an expense.

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    Re: Yellow stains on fiberglass

    Hi again. Sorry for the delayed reply, we continue to suffer through our nightmare pool experience (story for another post!). We recently had to drain the pool for an inspector, which is why I'm so delayed in following up on this. When it was drained, we tried rubbing vitamin C on the yellow stains but with no luck. The pool was recently refilled and we had the water tested several days later (with good results) and the yellow staining continues to get worse. Not sure what #s you need from the test results, but here are a few:
    CYA 11
    TDS 400
    PH 7.5
    Tot alkalinity 116
    Tot hardness 193
    Mustard, green or black algae None
    Thanks!
    10k gallon fiberglass freeform pool, Paramount SwingJet system, Dolphin DX5 robot, Pentair 48" Tagelus sand filter with glass media, WhisperFlo 1 HP pump, Hayward H200FDN natural gas heater, TF-100 Test Kit, and, of course, Margaritaville Tahiti blender!

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    Re: Yellow stains on fiberglass

    While I can't help on the source of the stains, I get them on my fiberglass stairs at the beginning of every season. I scrub them out with a Mr. Clean Magic Eraser then they're gone for the rest of the season. I'm not sure if this is an option for you if the entire pool is stained.
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    Re: Yellow stains on fiberglass

    Hi. Thanks for the reply. We use Magic Erasers on our waterline and they work great. I did try it on the stains when the pool was recently drained but they did not get rid of the stains. I am at a complete loss as to what is causing this and how to correct it.
    10k gallon fiberglass freeform pool, Paramount SwingJet system, Dolphin DX5 robot, Pentair 48" Tagelus sand filter with glass media, WhisperFlo 1 HP pump, Hayward H200FDN natural gas heater, TF-100 Test Kit, and, of course, Margaritaville Tahiti blender!

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    Butterfly's Avatar
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    Re: Yellow stains on fiberglass

    What is the source of your fill water?

    Have you had fill water tested for metals?

    Did you previously use sequesterants?

    Was the pH ever allowed to get high?

    Was the pH ever allowed to get below 7?

    Do you have a heater that contains copper?

    What daily level pH did you maintain?

    Please add your location in your profile.

    Sorry for all the ?'s , just trying to help
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    Re: Yellow stains on fiberglass

    Hi. No worries on all the questions, appreciate the help. The water was from a spring water / pool water supplier. I did have it tested for metals, the report said none. I don't know what my daily PH level is, sorry. We are in Northeastern, MA. We do have a heater, but I don't know the answer to the copper question. We have a heater (Hayward natural gas) but have only run the heater a few times this yr. Not sure what a 'sequestrant' is, sorry.
    10k gallon fiberglass freeform pool, Paramount SwingJet system, Dolphin DX5 robot, Pentair 48" Tagelus sand filter with glass media, WhisperFlo 1 HP pump, Hayward H200FDN natural gas heater, TF-100 Test Kit, and, of course, Margaritaville Tahiti blender!

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    Butterfly's Avatar
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    Re: Yellow stains on fiberglass

    If you don't have one of the recommended test kits, you need to order one. Also, the speed stir is very helpful, esp w/the CH tests. Test kits are compared in Pool School. The fav is the TF100, link in my sig. This will get you on the right path.


    They said no metals, but it sounds like metals.
    Try this, instead of just rubbing the vit C tabs on the stain:
    Crush some cheap vit c tabs in a sock and hold it on a stain for a few minutes and see if it lightens.

    When did you have if refilled with the new water ?

    What are current test results? (The other tests did not contain FC or CC or TC. Also, there is no way to test CYA at 11. Sounds like they just made up a #)

    Can you post some pics for us?
    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. ~

    If you found TFP helpful and we saved you money ... Become a TFP Supporter!

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    Butterfly's Avatar
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    Re: Yellow stains on fiberglass

    btw, did you have your fill water tested for metals? I mean the fill water that comes out of the water hose you use to top off.
    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. ~

    If you found TFP helpful and we saved you money ... Become a TFP Supporter!

  12. Back To Top    #12

    Re: Yellow stains on fiberglass

    Hi again. SO sorry for the delay, we had a dual birthday party for the kids this weekend which took up a good deal of time the past few days preparing!

    We did buy a better test kit this weekend, so I can now try to give you more numbers. PH was about 7.6 on Saturday.

    We had it refilled with water on 5/18 and the test results I sent before were from 5/24/13. We did not need any top off water at the time.

    That's disturbing to know they may have made up the CYA 11 number. Their test system is via Bioguard and provides a detailed printout. During that test, total and free chlorine were .7 and .6, respectively.

    While buying the test kit and a few other things this weekend, we did buy 'Super Erase' stain remover at our local pool store. We applied it and have been running the pump/filter continuously since then. I can't yet comment on how the stains look as the kids' pool party was yesterday, but will take a look tonight when I get home.

    Thank you again for your help!!
    10k gallon fiberglass freeform pool, Paramount SwingJet system, Dolphin DX5 robot, Pentair 48" Tagelus sand filter with glass media, WhisperFlo 1 HP pump, Hayward H200FDN natural gas heater, TF-100 Test Kit, and, of course, Margaritaville Tahiti blender!

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