Last season I had problems with stains on my liner from time to time when the pH got too high (from the SWG). I bought a couple of packets of Culator to test towards the end of the swimming season. It worked great for me. In fact, I just ordered several packets today for this season. One note though, once the stains are on the liner, I found that I needed to treat with ascorbic acid to release the stains. The culator worked well enough that the stains never came back (even when I let the chlorine and/or pH get too high). I only make this comment because you might save yourself a lot of work by putting 1 or more culator packets in the pool when first filling with the well water to prevent the metal stains in the first place.