CYA off chart...high?

[PoolDoc]

You can test with a vitamin C (ascorbic acid) tablet -- it will usually lift (re-dissolve) copper or iron. You'll need to let your chlorine drop to, say, 10 ppm before you try that, though. Chlorine destroys ascorbic acid.

That's OK, though. There's no reason to have FC = 35, unless you have some algae. (If you do, brush at it, and it will probably be gone by the them chlorine levels drop.

[reacherAZ]

I've decided to wait on AA process until after pool drain/refill in a month or so. Ideally, my CYA 170, & CH 750 will both be at better levels then...fill water tested at 250 CH. I will test vitamin C on stains once FC comes down, however. I should probably look at heater condition, as well...fairly certain it is original 1997 (RayPak RP2100.) No algae issues since FC levels up.

[PoolDoc]

If you have a heater, then you may have copper stains from low pH eroding copper from the heat exchanger. This is quite common on pool where trichlor has been used, and owners weren't diligent to maintain pH > 7.2