I have been lurking around here for 4 yrs and love this site. Sadly, I have an unusually difficult one to post.
6 mos ago I discovered brown/black "spots" on the pool steps and certain areas on the floor. About the size of a pin head or a bit larger (irregular shape). Scraping with a thumb nail did little, although some of them were raised enough to scrape off the top and leave the brown/black color on the white plaster surface. No smearing, or wet appearance upon actual scraping. Bone dry, more like scale but raised.
Expected the usual suspects. SLAMMED the pool for 10 days, rubbed with 3" puck 3 days straight, and even used metal brush 3 x's / day for 10 days. Not even a slight fading of the spots. Left 3" puck weighted down sit on spots overnight and still no fading. Figured this must be in-organic. Took a sock full of crushed Vit C tablets and rubbed for 5 mins, nothing. Left the full sock, weighted down, on an area overnight (do not try this at home because it will discolor your white plaster), but still absolutely no effect. Rubbed again with individual tables using them like mini pumice stones. Nothing, totally impervious to CL or citrus acid.
So now I am at a total loss. 30,000 gallons white plaster pool. TA-30. pH-7.3. FC-12. CYA-35. TC-12. CC-0 Would appreciate any sage advise...
6 mos ago I discovered brown/black "spots" on the pool steps and certain areas on the floor. About the size of a pin head or a bit larger (irregular shape). Scraping with a thumb nail did little, although some of them were raised enough to scrape off the top and leave the brown/black color on the white plaster surface. No smearing, or wet appearance upon actual scraping. Bone dry, more like scale but raised.
Expected the usual suspects. SLAMMED the pool for 10 days, rubbed with 3" puck 3 days straight, and even used metal brush 3 x's / day for 10 days. Not even a slight fading of the spots. Left 3" puck weighted down sit on spots overnight and still no fading. Figured this must be in-organic. Took a sock full of crushed Vit C tablets and rubbed for 5 mins, nothing. Left the full sock, weighted down, on an area overnight (do not try this at home because it will discolor your white plaster), but still absolutely no effect. Rubbed again with individual tables using them like mini pumice stones. Nothing, totally impervious to CL or citrus acid.
So now I am at a total loss. 30,000 gallons white plaster pool. TA-30. pH-7.3. FC-12. CYA-35. TC-12. CC-0 Would appreciate any sage advise...
