I bought a house with a 30+ year old pool at the end of the season last year. It had some slight staining on the plaster, which I planned to deal with this year when the pool was opened again.
The staining has gotten much worse and is covering a lot of the sides and bottom of the pool. It is a light green/grey/brownish color. We has shocked the pool and the water is very clear. The pH was very high and we use well water, so I suspected metal staining after reading some threads on this forum. The pH is corrected to normal levels (7.8). We have tried scrubbing by hand with no luck. I tried some Vitamin C tablets today with very bad results - a big black streak and the original stain is still there under the black.
A couple of pics are attached showing stain and then stain after Vitamin C tabs. Any help anyone can offer would be greatly appreciated.