As my user name implies, I didn't know jack about pools until 10 months ago when I bought a house with one. Everything I know about pools I have googled or have lurked it here. I am posting a new thread about my liner staining issue, not sure which category to put it in but y'all will see it. So far I have done a lot to my pool. I have replaced an old centurion triton pump with a Hayward variable speed programmable. By the way, I did all of this myself. I don't believe in paying someone for something i can read about and learn how to do. I have replaced the de filter grids, replaced some 3 way diverter valves, replaced some leaking plumbing and valves, and a few small things not worth mentioning. So, you can see I am a hands on kind of guy.
Kudos for doing so much on your own already. 
That's fantastic. Item #1, how are you testing your water? Hopefully with a TF-100 or Taylor K-2006. As for your staining issues, it could be metal (iron) in the water, but may be too early to tell. A couple tests you can do .... gently hold a chlorine tab on the stain for a short bit, but keep it moving to not damage the liner (organic). You can also take some crushed vitamin C tablets (in a sock or something) and hold those to the stain (metals). Let us know if either of those methods works. You can also can check with your water company and/or take a fresh sample of fill water from your hose to the pool store to see what they come-up with. Let us know please. Great to have you with us.
