Newbie - Stain removal via ascorbic acid

[Watermom]

Herb, I asked Ben to take a look at this thread for you.

[PoolDoc]

Sorry, I missed the fact that you'd gotten the testing done.

I rescanned this entire long thread. There's a lot here that doesn't make sense.

For example, your pool's CYA levels did NOT suddenly drop from 70 - 100 ppm to 25 - 35 ppm, unless you dumped over half your water, and refilled. So, we're missing data here.

Did you change pool stores? Test in a different way? Or ??

Regarding the stains, we've got more mysteries. Now that you've established that your pool store can tell the difference between water with no copper, and with 0.2 ppm, we've got an issue. It would seem that your pool water has 0.2 ppm . . . copper is STILL getting into your pool. I suppose that it's possible that copper is leaching from the side walls. But it sounds more like it's accumulating on the walls. But, if you've been using cal hypo, you should have been removing copper on your filter. (What color has your backwash or filter goo been?)

Unfortunately, there's some underlying chemistry here that I don't understand well -- and if anyone else does, they haven't published in a location where I've seen it! Questions like:
How well can various pool wall surfaces 'store' copper?
Will copper in wall surfaces change from soluble (no stain) to insoluble forms and back?

I can only see two possibilities here:

1. You are still adding copper to the pool, somehow. You could test your tap water, this time and see if it has copper. That would be unusual, but a matter for concern if it is true. Potable water that corrodes copper, will also leach lead into the water. It's rare these days for a public utility to run water that will do that, but I suppose it's possible. Or perhaps you're on a private system?

2. Your original dose of copper (still not really explained) was MASSIVE, and you've 'stored' a bunch of copper in the water and in the walls that's showing up again as the sequestrants break down.

At this point, the first thing to do is eliminate possibility #1, and make 100% sure no new copper is entering the pool.

Then, lower the pH, add sequestrant, and drain!

Sorry, to have to say that, but I'm not sure, given the persistence of the copper in your pool, that there's any choice.

When you drain, you'll need to be careful. First, you can only drain if it's a concrete pool. But, you said it's painted, so I assume it's concrete. Second, you can only drain if the ground is dry enough, so the pool won't float out of the ground. If you are from the Nashville area . . . don't drain till it dries up, a lot. Third, you need to be careful where the water goes. Unlike chlorine, copper is a persistent biocide, and will kill fish and other aquatic life. You don't want your drainage to dump into a stream, leading to a fish kill that brings enforcement folk to your doorstep.

Good luck,

Ben

PS. If there's copper IN the walls, there's no guarantee that it will all be gone from the walls when you drain. So, it's possible that when you refill, some of the staining will reappear. Hopefully not, and I have repeatedly seen copper stains lift over time (unlike iron stains). But, just be prepared. If you want to be sure of no stains, you'll have to repaint.