Help! - Dark Stains on Vinyl Liner and Plastic Fittings

We have an inground pool with a vinyl liner. It's been nice and clear for years. About a year ago we installed a Hayward heater. 6 Months later the heater core started leaking and the copper in it had disolved due to low PH Hayward told us (they were quite good to deal with by the way). This year for the first time, we've had grayish/black stains appear more and more frequently randomly around the pool. Out plastic skimmer and bottom drain have also turned dark for the first time. The pool water is superb however - no cloudiness and perfectly balanced now. Shocking the pool with high chorine level seems to help, but they come back quickly. We got a stain eraser and it has no effect at all on the stains. I suspect we have copper in our water from the heater core portion that disolved which may be the root of the problem. Any idea how to get rid of these stains...?

You will need to put a sequestering agent in the water. Take your ph down to 7.2, put in the sequestering agent and let the water filter 24/7. If the stains don't lighten, then you will have to use an ascorbic acid stain treatment. Read through the metal forum, and it should explain more for you. If you have any questions, just ask.

Thanks, Marie!
Can you suggest a Sequestering agent? I am completely new to this.
Regards,
-Howard

Jack's Magic, Sequasol, Metal Free, there are many out there - these are the ones I have used in the past.