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.
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.