New member here, but I've read the forums for a couple of years. I'm having trouble with brown stains on the steps and walls of my pool. It initially started on the steps, and recently has become noticeable on the walls as well. See the pictures below. What's causing these stains and how can I get rid of them? The plaster is about 3.5 years old.
Here's the chemistry readings as of this afternoon (using a Taylor K-2006 kit):
FC 5.5 ppm
CC <0.5 ppm
TA 100 ppm
CH 480 ppm
I couldn't get a CYA reading because I just ran out of the reagent. I'll order more.
One other note that may or may not be related: the pool seems to need a LOT of acid. I usually have to add 0.5-1qts of acid every 2-4 days, and even then the pH is usually between 7.8 and 8.0 when I test it.