Fiberglass pool has calcium buildup.

Fungi

Well-known member
May 5, 2015
53
Central Illinois
So I screwed up. I opened the pool, added the stabilizer, but never lowered my alkalinity, and I let the ph drift high. Due to medical reasons we only used the pool 4 times all summer. I kept the chlorine at 1-3ppm, but I now have a thick layer of calcium buildup on the fiberglass pool walls. Would it be possible to fill the pool with soft water and keep the ph below 7 long enough to disolve the calcium then drain. Manually removing using power washer or sand blaster has been recommended, but beyond my ability right now. Any advise?

calcium-01.jpg
 

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Texas Splash

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Curious ... have you confirmed the chalkiness is calcium? Maybe it's just me looking at the pic, but Is the pool currently empty? If empty, pour a small amount of muriatic acid on that top step. If it's calcium, it should fizzle. If it doesn't, then it's a whloe different issue.
 

Fungi

Well-known member
May 5, 2015
53
Central Illinois
Hi TS thanks for the reply. I just checked and it fizzes like crazy. The pool is empty. It's on a hillside with a water shedding roof, and a sand foundation 80' above the water table.
 

Dirk

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Nov 12, 2017
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Based on a bad experience, I don't recommend an acid wash for a plaster pool. But in this case... can a fiberglass pool be acid washed? I'm not sure who to ask about that. Pat?
 

Texas Splash

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The only thing about maintaining aggressive water (i.e. low CSI) is that the results may not be uniform across the entire pool. It wilt also take a while, coupled with aggressive brushing. There is also a no drain acid wash process that some plaster pool owners try, but it requires careful application since making the pH crash to around 4 ppm can cause other problems for a pool or its surfaces. The other thought, besides what you noted above already, would be sanding/buffing the gelcoat while it's empty. But I suspect you're about to close right? I'm guessing to prepare for winter and to prevent potential shell "floating" you are going to fill back up right away?
 

Fungi

Well-known member
May 5, 2015
53
Central Illinois
Thanks for the reply Dirk, I hope there is a way to remove this easily.

Thanks TS, I was thinking to reverse the procedure that created the calcium deposits. I was going to shoot for a ph of 6 and let it go for a few weeks next spring. I am in a situation that should allow for draining everything bone dry for the winter. I am sick of opening a pool of death soup because some mice drown over the winter. With such a small pool it stinks so bad. I usually have to drain and refill every spring. Because of the fact that the pool is sitting in bone dry sand that cannot get wet from precipitation I don't see the concern. I've drained it completely after getting 6 inches of rain without issue because the rain water doesn't get to the ground around the pool. Polycarbonate roof panels.

If I have to hire someone so be it. There is no way I can do the labor part due to illness.

Anyone have any first hand experience with this problem?
 
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duraleigh

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Apr 1, 2007
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No first hand experience but if it was my pool and in your condition I would suggest exactly what you posted in the beginning.

I would drop the pH to 6.8 and keep it there......checking pH twice daily because you don't want to go lower or higher. CH of 150 should be fine or possibly a little higher.

Have someone brush the pool surface with a stiff (not metal) brush every couple of days or so. I believe the calcium will go back into solution and you will be out very little except for a little elbow grease.
 

Texas Splash

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Jim, while an elevated water table may not be an issue for you, I wanted to give you a few other things to consider should you try to keep water in the pool and make the water aggressive to remove scale:
- If you refill, I expect you would still need to winterize which would mean a lower water level to clear the lines. That could lead to uneven scale removal.
- With a winterized pool, you would have no way to keep water moving through the lines and skimmer which could be a problem (freezing)
- In your area, the TA is usually exceptionally high. Not uncommon to see it pushing 300-400 or more. Perhaps you already know your normal TA, but if it is that high, it could make maintaining a lower pH a bit problematic requiring more acid treatments.
- With a winterized pool, it would be difficult to mix acid across the body of water.

Those are just some things that popped into my head later as I thought about your situation. Just wanted to ensure you looked at every angle. Have a good day.
 

duraleigh

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I agree with Pat. If you intend to winterize, I would simply not even attempt ANY approach at removing the calcium until you can refill the pool completely.

Even if you kept the pool open until December, I am not sure that would be long enough to remove that calcium. Sounds like a spring time process to me.