Fiberglass pool badly stained

So glad you guys are back :)

Might as well be among the first of the needy !

Background, have a small fiberglass pool that uses a heat exchanger and a zone off our our boiler for heat. Works great. Last year I noticed that below the water line was becoming stained and couldn't figure out why. Tried metal out, jack's magic and a couple of other products with no results. Fast forward to now, pool is drained down about 1/3 and the staining is really bad, about the color of oak from the water line down. Figured I'd try some muriatic acid on a test area and it worked great for bringing it almost back to white. Gave the test area a good rinse when I was done.

I found the source of the metal and it was a couple of galvanized pipe elbows off the heat exhanger, they were very badly corroded inside. Replace them with pvc.

Well that a lot of baggage but there are a couple of questions coming:

I want to drain the pool, dry it, spray it with acid, rinse it and then refill it. Not much ground water underneath me, yard is quite sloped and the pool is at about mid yard. Anything to be aware of when draining it?

Next, muriatic acid and fiberglass, good idea or bad idea? Any precautions other than glasses, gloves and ventilation?

Last one, I'm sure there'll be some metal in the water still when I'm done, how can I get that out and prevent staining in the future?

Thanks for any help.

Mark

Hi, Mark,

Interesting problem. I will be using a heat exchanger this Spring, as well. I'll pay careful attention to the metal issue.

I'd get an opinion from a Fibreglas pool manufacturer about draining. Perhaps there's a way you can do a 90% drain and be a little safer. I wouldn't do it at all 'til I got a consensus from the fibreglas folks.:(

Ditto advice on muriatic to clean fibreglas. Good idea, just make sure it won't eat your pool:(

Not sure I understand your concern about future metal. If the galvanized was the source, and you eliminated it, why do you believe you'll still have metal content when you refill with new water?:confused:


Dave S.

Thanks Dave. I'm not getting too far with the manufacturer unfortunately so looking for the advice of the experienced folks here.

When you hook up your heat exchanger, make sure you use schedule 80 pvc, the regular stuff can't take the expansion of the heat exchanger and starts to leak, that's why galvie was put in mine and it was a bad move.

As far a metal content goes-- just don't want to have to go through this again so want to make certain that any old water or metal that's sitting in pipes, filter sand, etc will not cause staining again.

Thanks,

Mark

Hi, Mark,

There's not too many fibreglas owners on the forum here so you may have to be patient. (I'm not one)

Did you use PVC on both the boiler and pool side of your exchanger? If so, what temp is your boiler water coming into the exchanger? I'm thinking I'll probably use brass and PEX on the hot side and PVC on the pool side.

Since the metal precipitated out onto your fibreglas and you have eliminated the source, I don't think you'll have any further problems

Is your exchanger copper or stainless? If it's copper (on the inside), faulty pH can eat up the copper pipes pretty quickly. Stainless is pretty bullet proof but can still have some fittings that are just black iron that can lead to issues like you've experienced.

Dave S.

Hi Dave,

Boilder side is copper going in and out of the exchanger. Water temp I think is about 190. Pool water connections going through the heat exchanger have been my greatest source of difficulty and leaking. Sched 40, expands and contracts too much and eventually the teflon tape fails and it starts to drip. Galvanized pipe worked great for leaking but dismal for pool staining, a lesson learned. Shed 80 pvc loaded with teflon tape has worked out pretty well so far.

My exchanger is all stainless, works great but wish I went a little larger, too much hot water exiting the exchanger back to the boiler so I believe larger exchanger would have transferred more heat. Shouldn't complain though, I can raise the pool temp about 1.5 degrees per hour with the current exchanger.

Mark

hoogie,

I have a 16k gallon fiberglass pool. I have never drained it completely since the manufacturer told me not to as it will void the lifetime structural warranty. While building the pool, this concerned me so much I kept inquired about draining further. I found out fiberglass pools can in fact be drained if:
1. There isn’t any ground water under the pool. Mine has an access lid (identical to the skimmer) with a 12” plastic pipe that extends to the bottom of the deep end. Builder said this was for pumping out/inspecting ground water in case the pool needed to be drained.
2. The walls MUST be braced. One of the workers told me they use “spacer jacks” like the ones used in the back of a tractor trailer to brace loads. I’m not exactly sure how often/how many braces must be used. This is apparently to prevent stress on the walls from the settling ground around the pool.

As duraleigh suggested, I’d get a manufactures advice. Keep pressing them. If the original is no help, try C&W pools in Joelton, TN (615) 256-7329. They have been making fiberglass pools for 40+ years. I’m sure they'll tell you don’t do it but it may be worth a try.

Have you tried using ascorbic acid? It has worked wonders for me in the past. It is available several ways. I generally use a product called Stain Free however I have noticed several other products out there. Anything that says ascorbic acid (a.k.a. vitam C) should do the trick. It is around $40 for a dosage that treats my $16k gallons and I get it at the local pool store. I end up treating once a season to remove metal stains. Definitely try this before you drain your pool. I found out about it here on the forum after spending $100 on Jack’s Crap to no avail. It worked perfectly on the first treatment. Good luck.

Thanks David, I'll check into that. It would be mint if I didn't have to drain it.

Mark

http://www.chemistrystore.com/Ascorbic_Acid.htm

The difference between food grade and not is that when they get it in the box form from the manufacturer it is food grade. Once they re-package it in smaller quantities, it can't be sold as food grade. I found this out because last summer they ran out of the non-foodgrade containers, and he called me to ask if I would take the bigger box.

It is the exact same product as the pool store "Ascorbix" and the like and much cheaper. However, Acorbic acid does not fix your problem, it only helps you return the stain to "a solution". A sequestering agent, which you will have to buy at the Pool Store will "hold it there".

Read the Pool Docs Thread regarding Metals and Staining. All pools are different. And I have not found one pool store or pool maintenance company here in Southeastern Mass. that even remotely understands the concepts of this Forum.

I have a 35,000 gallon vinyl lined pool with a heater.My metal comes from my fill water, which is a well. The fill water has a very low PH {5.5}and High Mangenese. I have a very hard time maintaining the PH at 7.0 in my pool.
I chlorinate my pool with nothing but sodium hydro chloride, using a liquimate feeder in a 5 gallon gerry can, and 1/2 to 1 gallon of 12.5 per night.
I never allow my stabilizer level to go over 40.
Filter is 6 hours on, 6 hours off. The liquimate adds just enough SHC to keep me chlorinated . This formula keeps me stain free until the squestering agent wears off, or my ph rises to 7.4, at which point the metal falls of solution and stains my liner. Then I add the acorbic acid, it magically disappears, and the circle remains unbroken.

Good luck to pool owners with wells.

Hi Hoogie,
I think I can help you. First, the staining you see is a symptom of a much more expensive problem - corrosion of your copper heat exchanger. Metal corrosion is caused by acidic water, or water that has too low pH, therefore too much acid. Remember that in a fiberglass pool, the pool surface does not alter the water chemistry at all. If you are using tablet form chlorine (3" or 1" tablet) this is likely the cause. These little tablets are really convenient, but very, very acidic. Tablet chlorine has a pH of 2.9 - a lemon for comparative only has a pH of 2.0!! So, as they dissolve, they drop acid into the water. In a fiberglass pool, the surface isn't dissolving alkalinity into the water (as plaster does) so there is nothing to counterbalance this effect.

First to prevent the problem, watch your pH carefully and adjust weekly to 7.6. This will protect your very expensive heat exchanger also. Your test kit will tell you that 7.2 is "normal" however, we are "reading colors" which is a subjective matter. Keeping your pH a tish on the high side is less destructive than on the low side of normal, and you have a cushion, just in case you go away and forget to check it. Low pH is very destructive!

Now, how to fix this problem?? Easy. You can, of course use muriatic acid on a fiberglass pool, provided it is a quality shell. If it is an Aloha Fiberglass Pool, there is no problem whatsoever. I can't speak for other manufacturers. Be careful, though, Muriatic acid is nasty stuff. Wear your protective gear if you use it. But, there is another product that is nealy 100% effective at removing the stains, then keeping them away- Metal Magic by Haviland. 800-333-0400. Unlike Jack's Magic, which works some of the time, but not all of the time, because it is a sequestrant, not a remover. The first time you suprchlorinate, you destroy the protection. We've had amazing success with Metal Magic.

To keep the stains away, keep that pH at 7.6 check weekly and adjust as needed. Keep a metal removing agent in the water at all times. Metal Magic is a good product for that.

Quote:

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Originally Posted by alohafiberglasspools

Hi Hoogie,

But, there is another product that is nealy 100% effective at removing the stains, then keeping them away- Metal Magic by Haviland. 800-333-0400. Unlike Jack's Magic, which works some of the time, but not all of the time, because it is a sequestrant, not a remover. The first time you suprchlorinate, you destroy the protection. We've had amazing success with Metal Magic.

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My builder gave me two bottles of Metal Magic for my fiberglass pool after putting one in himself. It was no more effective than Jack's purple stuff that I also used. Looking up the MSDS for both products I found that they are both phosphonic acid derivatives as are the majority of stain and metal products on the market. My problem was a bit of rust staining and some concrete that hardened on the steps of the pool from the construction phase. The staining disappeard right away but the builder is still trying to get rid of the concrete! I think his theory was the low pH caused by these types of products would help dissolve the concrete.