I have a yellowish stain on my Krystal Krete pool. I'm fairly certain it's stain, not algae because:
-- it doesn't scrub off
-- it has responded to a stain-analysis test (responds to iron)
-- stain-removal products have helped somewhat in the past
Each time I've treated I've used Pinch-A-Penny products (actually made by Jack's Magic) -- 'Iron and Cobalt Stain Removal', used with 'Ultimate Metal Control Plus' (a sequestrant), plus chlorine neutralizer necessary for the stain remover. It's expensive -- each process comes to about $75.
A few years ago the stain treatments may have lightened the stains about 80%, but not entirely, and the number of spots has grown substantially.
The stain removal product says it should be used with TDS <= 1,200 ppm, whereas my TDS is 2,900.
I called in a company who acid-washed a friend's pool at a fair price with great results. The fellow who came looked at the stains and said I'd be wasting money because from experience he knows acid-washing won't remove this stain, though he couldn't tell me what the stain is. (The company also does pool resurfacing, so I could be suspicious that they'd prefer to resurface, but my friend didn't get any such redirection and they have high marks on Angie's list.)
Present chemistry measured by Pinch-A-Penny is:
Total Cl = 3.0 ppm
Free Cl = 3.0 ppm
PH = 7.5
TA = 85 ppm
CH = 250 ppm
TDS = 2,900 ppm
Salt = 2,000 ppm
Stabilizer = 60 ppm
The Krystal Krete has been in place since before I bought the house 8 years ago. (We love the Krystal Krete color and surface.)
So, I'd appreciate all advice. Can this be solved or am I likely to have to resurface? If it can be solved, how?