MAJOR iron Stains...need any advice you can give!

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hlh1978

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May 2, 2010
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Hello. We puchased our home with a gunite pool about three years ago and noticed some discoloration on the sides. At the time, knowing the pool was 25 years old and unsure if it had been replastered or not, we had a pool company come out and take a look at the plaster. He said it was the gunite showing through and we needed the pool replasted at a price of $17,000. (Fast forward two years and A LOT more staining, brown stains cover 75-80% of pool walls) Thanks to the internet and the magical vitamin C test, we discovered that is was not the gunite showing but iron stains. Ok, so off to the pool store for some ascorbic acid. Here's what we did based on our pool store's instructions:

Pool size: 55,000 gallon gunite pool.
Day 1:
Drop chlorine to less than 1 ppm-- Check
Add 3 bottles of Ascorbic Acid to pool (sprinkle around sides) -- Check
Brush -- check
Run pump on FILTER continously (may take up to one week for stains to lift) --Check
(*We are now at day three and while stains look better, still there, so we added another 3 bottles of AA)
Day 4: Still have stains/only slight improvement
Day 5: No improvement in stains - added 2 bottles of metal free and filter aid per pool store's instructions. Backwashed pump --check
Had water tested ph at 7.4 (Said all other numbers were perfect and my metal was at 0.1)


NOW WHAT--should I do another AA treatment? If yes, what is your recommended dose and when do I add the metal sequestrant. Some have said keep addding AA until stains are gone. Oh, I should ask is Metal Free a metal sequestrant?

OR Should I bring chlorine back up and know that this is about as good as it will get?

OR should I drain it and do an acid wash?

OR should I try a different acid, like citric or oxyalic acid?

I'm at a loss at this point and really, really need help! Thanks in advance.
 
Hi there,

I hope you added Polyquat 60 as an algaecide preventative.... this is an important step in the process.

Proteam Metal Magic, Jack's Magic and GLB Sequa Sol are three good sequesterants. Metal Free is not.

If you haven't added PQ 60 I would do so ASAP.

You have to ask yourself if you can live with the staining as is? Its a personal preference sort of thing. Do you want to continue with the process even though it may not get any better, or can you live with it?
 
I did not add Poly60. The pool place mentioned nothing about it. How much should I add?

Can I live with the stains? I would prefer not to. That said, I don't want to throw money at something that's not going to get any better.

About the metal sequestrant...do I need to add that at the same time as the AA or wait 24 hours?
 
If the stains are very extensive and old, it may take quite a bit of ascorbic acid to remove them all.

Sequestrant can occasionally help remove stains without any AA involved, but it almost never works when used alone on older stains. Opinions differ on using AA first and then adding sequestrant, or using the two together. There seem to be pros and cons to each approach, none large.

Metal Free is a sequestrant, but it is not one of our recommended sequestrants. It works, but sequestrants based on phosphonic acid or HEDP are much more effective.

Citric acid is less expensive even after accounting for the need to use twice as much compared. But it won't work better or worse than ascorbic acid. Oxyalix acid is slightly more dangerous to handle, but occasionally works either better or worse depending on details that are difficult to predict.

One thing you can do as a quick double check is to try the vitamin C test again, rest a vitamin C tablet on a stained area for 30 seconds and see what happens. If vitamin C helps, then you just need more AA.
 
Could you post some pictures? If the gunite is exposed (bad!), the iron causing your staining could be leaching from the rebar. In that case, replastering and refilling would solve your problem, but AA treatments wouldn't fix the root issue.
 
Also, what is your water temperature. The lower the temp the longer it takes. I did mine in fall when water temps were in low 70's and it probably could have gone longer than 2 weeks but the dogs were insisting on swimming.

Please add the Poylquat 60 (or similar) to avoid algae.

BTW..... I added more than double the AA over a weeks time. It's a lot cheaper to order it from Amazon in crystal form.

I kept my pH at 7.2. Let's let the experts advise on that. It might speed up some with pH a little lower.

I, also, kept my pH at or only a little above for the whole winter and used a lot of sequestrate over the winter. My iron comes from the sand/silt/dust that is carried in by the dogs and blown in.

I had a lot of scaling (I could tell it was scale more easily because my plaster is blue) that held the stains more strongly than the plaster did. Over the winter the scale actually lifted some.

gg=alice
 
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