This is my second year with the pool but now I have stains on the stairs which I didn't have previously (see dark areas of stairs). The stains are brownish and they do not respond to ascorbic acid. They don't come off with a stainless steel brush either, but a pumice stone works (if you look at the upper right corner of the stairs you can see lines from using the pumice stone). The problem using a pumice stone is that I have 3 stairs and they're wide!
If someone could help me determine the cause of the stains and suggest a relatively quick way to get rid of them I would appreciate it! The pool is open year-round. I get quite a bit of dust on the stairs and have to brush them every couple of days. Also, I inherited a high calcium level (originally over 600) which I'm working on and have brought down a bit. Here are my latest test results:
Should I shock for a few days? Haven't done that in a while.