Hi, over the course of the past 3 years our pool plaster developed some brownish discolorations, predominantly on the vertical parts, pictures attached.
Plaster 001.jpgPlaster 002.jpgPlaster 003.jpg
Also the plastic return nozzles started turning brown. It does not look like a deposit, but a discoloration of the plaster itself. It cannot be brushed off and I tried ascorbic acid without success. Not sure how old the plaster is, as we bought the house just 3 years ago, but I would assume 5-8 years.
Pool chemistry: Typically we have FC 2-4 with CYA 30-40. pH has not always been immediately addressed when turning high. so we had longer periods with 7.8-8.2, but try to maintain 7.5-7.8 TA was typically at the low end with 70-80, CH as well with 180-210. We did not bother too much about phosphates in the past and stopped dosing Anti-Phos, so this went up to about 1,000.
Any ideas / suggestions are welcome.