Thanks to both of you for the prompt reply. I left alot of info out ,sorry.
The pool is 15 years old 16X32 approx.23,000 gal.,still on the original vinyl liner. I started on Bauqasil when it was new and switched to chlorine 7 years later (glad) . Added a heater 3 years ago. I have had very few water problems using the baking soda and borax. I use bleach when I open the pool and a chlorinator with 1" tabs during the season.
When I opened the pool this spring the liner,steps ,etc were stained a brown rust color bad.Brushing did nothing to remove it.After reading your posts and information in the forum (great help). I ground some vit C tablets and tried it, the stain wiped right off. With help from the forum I determined the unbalanced water was eating the heat exchange and putting copper in the pool.I did the AA treatment several weeks ago and wow the pool looked great almost lke new(well almost) .I added the sequestor 2 qts of sequa-sol . Used bleach to bring the level up slow and the soda and borax for the PH and Alk.Everything looked good till this week and I noticed the stain coming back .We did have a family outing last week,lots of kids in the pool.The chlorine level was low so I added bleach to bring it up , I put a gallon in and the reading I took was 5-10 with my kit. It went down 2 days later. I was working on the PH and Alk when the stain started to re-appear. Never liked my hth test kit so I ordered a Taylor K-2006 kit. Using the new kit my numbers are FC 1,TC 1.5,CYA 120,TA 110,CH 210, PH 7.
I think you answered most of my questions and will be following your suggested route. It's not practical for me drain and add I'm on well water.
One thing,how does the CYA raise ? What is the range that is acceptable? Thanks again for all your help ,the forum is a great place to learn. I hope I can contribute with experiences I have had with my pool.