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Thread: Fiberglass pool with blisters-Bleach is the cause?

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    plucky71's Avatar
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    Fiberglass pool with blisters-Bleach is the cause?

    I'm not sure where to post this topic? Sorry if it shouldn't be here.

    Well I successfully used the BBB method for a complete season that started with a completely green swamp for a pool. So I thought that was a good thing until today. Now I'm questioning it? I talked with the manufacturer of my fiberglass pool. I described some blisters that I have on/under the surface of my pool. The first question he asked is if I am using liquid chlorine/shock for my sanitizer. I was so surprised.

    Of course I said yes, and He said that(liquid bleach/chlorine) is the problem. I don't know why, but He said that over 15 years of experience has shown that to be true with Sun fiberglass pools. That is the brand I have. I asked what other possibilities. He said it could have been something to do with the manufacturing process.

    I am new to owning this pool. Maybe the blisters were there before? Maybe they weren't? Maybe they were not that bad this spring and they got worse over the summer. I don't know, but I am certainly disappointed at the thought that I might have to stop using liquid shock as my sanitizer. My main source this year was pool store shock 10% I was paying $10 for four gallons.

    Anyway, does anyone have any thoughts on the subject as I consider next year?

    As a side note, they recommend using two pucks every 10 to 14 days at a setting of 2 of 5. Target FC level of 1.0 ppm. And then Calcium hypo like once a week. I am just confused and disappointed at this point.

    BBB and this forum has been great this year. I realize if I have to switch to pucks and powder shock that I will still use my good test kit and the good knowledge of this forum.

    Thanks for listening to my problems.
    Outdoor fiberglass inground 15,000 gallons, Clean & Clear Plus 420ft. sq. filter, 1 h.p. WhisperFlo pump, New water cycler automatic chlorinater(not using), 1996 pool, TF-100 test kit.

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    Re: Fiberglass pool with blisters-Bleach is the cause?

    Call me skeptical, but I just don't buy it Maintaing an FC of 1 as is being suggested to you makes no sense and how can acidic pucks be any better? With an FC of 1, algae outbreaks are almost guaranteed and constant shocking has to do more damage than just mainating FC. I don't agree, but if you choose to follow their advice, continue to follow the FC/CYA chart and be prepared for occasional drain/fills to keep CYA and CH in check.

    I guess the manufacturer can state what they want, but unless the use of liquid chlorine is explicitly stated in your warranty paperwork, I wouldn't switch. Just MHO.
    24'x52" AGP (13,500 Gallons), Intex SWG, (2)Solar Bear 4x20 panels, Hayward S220T Filter, 1/2hp Pentair Superflo

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    Re: Fiberglass pool with blisters-Bleach is the cause?

    Oh no, so all the fibreglass pools in the entire world using chlorine are going to blister!
    It's osmosis of the fibreglass and happens to fibreglass boats too and they are in salt water most of the time not chlorine.
    Just another freekin lie!

    Almost forgot, how many glassfibre filter casses are there, do they blister?

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    Re: Fiberglass pool with blisters-Bleach is the cause?

    Is the blistering only in the area where you added the chlorine? Did you add chlorine slowly over a return flow with the pump running?
    16,000 gallon outdoor in-ground 16'x32' plaster pool; Pentair Intelliflo VF pump; Pentair IntelliTouch i9+3s control system; Jandy CL-340 square foot cartridge filter
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    Re: Fiberglass pool with blisters-Bleach is the cause?

    We run wet chlorine through fiberglass piping so I'm not sure I believe the liquid chlorine caused the problems. I suspect it's something else.
    Dave J. TFP Moderator
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    Re: Fiberglass pool with blisters-Bleach is the cause?

    Quote Originally Posted by chem geek
    Is the blistering only in the area where you added the chlorine? Did you add chlorine slowly over a return flow with the pump running?
    No, the blistering is throughout. On some walls and on the bottom. Yes, I did add it slowly over a return with the pump flowing.

    I am also skeptical, it just really threw me off when his very first question was about liquid chlorine.
    Outdoor fiberglass inground 15,000 gallons, Clean & Clear Plus 420ft. sq. filter, 1 h.p. WhisperFlo pump, New water cycler automatic chlorinater(not using), 1996 pool, TF-100 test kit.

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    Re: Fiberglass pool with blisters-Bleach is the cause?

    Do a Google search for Fiberglass Osmotic Blisters. Some fiberglass boats that sit in the water for long periods get the same blisters. The way pools are manufactured is nearly identical to boat hulls.
    15' x 30' Rectangular, 6 ' deep end; 30 year old in-ground - ~15,000 gal.; Gunite/plaster pool surface; Screened in "Florida Room"/cage over the entire pool; Cool Deck patio surface; 3/4 hp Magnetek Pump motor; 1-1/2" PVC plumbing w/ 2 returns; Pentair Clean & Clear 150 sf cartridge filter; Baker Hydro Skimmer & separate dedicated vacuum port; Sta-rite Great White cleaner; TF100 Test Kit. & BBB chemicals

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    Re: Fiberglass pool with blisters-Bleach is the cause?

    Quote Originally Posted by Bayport_Bob
    Do a Google search for Fiberglass Osmotic Blisters. Some fiberglass boats that sit in the water for long periods get the same blisters. The way pools are manufactured is nearly identical to boat hulls.
    Thanks, I will do that.
    Outdoor fiberglass inground 15,000 gallons, Clean & Clear Plus 420ft. sq. filter, 1 h.p. WhisperFlo pump, New water cycler automatic chlorinater(not using), 1996 pool, TF-100 test kit.

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    Re: Fiberglass pool with blisters-Bleach is the cause?

    Check calcium level if it is to low it will blister your fiberglass.
    CPO for a water park, 850,000 gals, liquid chlorine.

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    Re: Fiberglass pool with blisters-Bleach is the cause?

    Check calcium level if it is to low it will blister your fiberglass.
    How low is too low? Is this stated somewhere in a manufacturere's info?
    Dave S.
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    Re: Fiberglass pool with blisters-Bleach is the cause?

    1st, it isn't the bleach. The gel coat is worn. Water penetration is breaking down the resin that binds the fiberglass.

    The pool needs to be refinished.

    Boat resins and pool resins are different. The construction method is similar for boats, pools, tables, etc... but the materials used are different.

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    Re: Fiberglass pool with blisters-Bleach is the cause?

    Thanks for the replies. It still is just weird that his very first question was "are you using liquid chlorine/shock".
    Outdoor fiberglass inground 15,000 gallons, Clean & Clear Plus 420ft. sq. filter, 1 h.p. WhisperFlo pump, New water cycler automatic chlorinater(not using), 1996 pool, TF-100 test kit.

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    Re: Fiberglass pool with blisters-Bleach is the cause?

    Some pool builders say the same thing about vinyl pools, swearing that the vinyl gets paper thin or wears out faster if you use chlorinating liquid or bleach. It is true that if you add any concentrated chemical in one place then it can potentially settle and do damage if it is denser than water and that is true for chlorinating liquid and bleach as well as acid until thoroughly mixed and this may be what they are seeing when some people add such chemicals themselves rather than using Trichlor in a feeder, for example (though if such a feeder parks itself in one place, the low pH is also bad for vinyl). Of course, it's also true for slow-dissolving solids like Cal-Hypo. However, adding a chemical slowly over a return flow to ensure thorough mixing and, if one wants extra protection, lightly brushing the side and bottom of the pool in the area the chemical is added results in identical chlorine in the water regardless of source. His recommending using Cal-Hypo on occasion would raise the CH level which is needed to protect the gelcoat in fiberglass as well as protecting plaster pools.

    If there were any problem with using bleach in either vinyl or fiberglass pools, we would have seen it in the thousands of pool owners reporting both here and on other forums over the last decade. There haven't been such reports. On this forum, this thread talks about fiberglass blistering on an existing pool (unlikely to have been on BBB as most pools aren't). On The PoolForum, this thread also talks fiberglass blistering on steps.

    If for the fiberglass pool the gelcoat has dissolved off or weakened, then that could be because the saturation index was not maintained, most likely due to low calcium hardness (CH). Do you recall the CH level in your pool during your last season using BBB?
    16,000 gallon outdoor in-ground 16'x32' plaster pool; Pentair Intelliflo VF pump; Pentair IntelliTouch i9+3s control system; Jandy CL-340 square foot cartridge filter
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    Re: Fiberglass pool with blisters-Bleach is the cause?

    Quote Originally Posted by plucky71
    Thanks for the replies. It still is just weird that his very first question was "are you using liquid chlorine/shock".
    Many questions....... what resins do they use?, how long are the pools cured for before being used (blisters seem to occur from pockets of un cured resin). Is the use of chemical tabs and not liquid mentioned in the owners handbook? why don't polyester resin/glass fibre filters blister or do they?
    Is the pool fit for purpose, based on most people using chlorine?

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