My pool builder suggested a commercial product (I don't want to give the name and be accused of spamming) that has a test kit for stains. I called that company direct and based on my explanation he said it sounds like calcium scaling and mineral deposits because when I opened the pool my PH was high (8+), which would cause the calcium to come out of solution and attach to the walls/steps. So I am going to pick up that test kit. Hopefully that confirms his theory or tells me exactly what it is and then we can treat it. He also asked if the stains were rough like sand paper and they are now that I went back and felt them, which also is consistant with calcium scaling.

I don't know what the treatment is for calcium scaling but hopefully it is fairly straight forward. I know it is pretty aggressive because you don't want to run it through the heater and I am pretty sure I don't have a heater bypass. So that will be a challenge.

Pool Doc thanks for responding. To answer your question - my house sat vacant from 2005 till 2009 when we bought. It also did not have a water softener. So the toilet tanks were very rusty when we bought. I have added iron out directly to the tanks and it cleaned them a lot, just not all the way. I have had my well water tested and the iron is at about .8 ppm, which .5 ppm or more will cause staining.

I will let you know what the testing confirms.