Quote Originally Posted by river-wear View Post
I figured it was iron, but for the sake of curiosity, what color are copper stains? Green?
Green, blue, black, grey, brown (copper color). Black and grey are the most common colors on fiberglass.
Here are the full test results for today:

Cl - zero again; added 1/2 gallon of 10% chlorine (sodium hypochlorite)
pH - 7.2 bring this up to 7.6 slowly once your stain treatment is finsihed and all stains are gone
alk - 60 bring it up to 70 ppm
Cal - 220 bring this up to 400
CYA - 50 bring this up to 80
salt - 2800ppm per test kit (AutoPilot says 3600...) What kind of test? I would tend to trust the Autopilot on this since that is what the cell is actually measuring. It's still withing the operational range so nothing to lose sleep over.

What are the desired levels for alkalinity and calcium?

There's still a puck in the skimmer and the chlorine generator is doing its thing, so I didn't want to add too much more of the liquid. I'll check on it again tomorrow. The water is clear and blue, but it feels like I'm tempting fate by writing that.

I still have a few stubborn stains in one spot, but all of the little speckles have disappeared now. Is there something you'd recommend for spot-treating?
Put some vitamin c tablets in an old white sock and hold them on the stains.
Thanks!
Hope this is helpful. The numbers I gave you above will have your water 'balanced' even if the pH drifts up to 8.0, which happens with SWGs so you should not have any bad scaling conditions. It is a bit aggressive at a pH of 7.2 but you want aggressive water when dealing with stains. At pH of 7.6 to 8.0 you are golden and that is where I would recommend you run the pool. Don't let the pH rise above 8.0 nor drop below 7.6 in normal operation and you will be golden.