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Thank you for your comments. I will get some calcium into the pool soon. I did read about the downsides of acid washing, but the stains are pretty ugly. I have sent pictures of them to the forum's email address and hope they will get posted for further consideration.
Haven't received any pictures at poolforum@gmail.com . . .
While your calcium is a little low, I'd hold off on adding any now. You're thinking about removing FAR more calcium with an acid wash, then you would with a year of slightly low calcium pool water.
But, get your pH up to at least 7.0. Then I'd recommend 3 things:
1. Try ascorbic acid in a sock on a badly stained area.
2. Also try "Iron Out" in a sock on a similar area.
3. And finally, tell me what Jack's chemical they are recommending: you may be able to get some THAT chemical in a bagged version somewhere, and try that before you get a bunch.
Good luck!
Thanks for the advice; I have raised the pH to 7.2 and FC to 6. There was no specific recommendation for Jack's chemicals, just that I visit their website. Jack has a treatment for copper stains but as I read it, the regimen for "the Copper and Scale Stain Stuff" would cost well over $200 and take the pool off-line for weeks. Don't think I want to do that.
I have resent the pictures to the gmail address.
I'm not sure what I'm seeing.
If the colors of the FIRST 2 pictures are correct, you may have copper staining + plaster mottling.
In the second 2 pictures it looks ONLY like plaster mottling, to me. The fact that you mention "brownish stains" in your first post make me think you ONLY have plaster mottling.
Plaster mottling is a defect in the plaster, possibly accentuated by water conditions. It's NOT a stain. Acid washing will tend to even the surface coloration, but at the cost of a more porous and abrasive exposed surface.
Here are some resources:
http://www.poolhelp.com/handouts/oB_...%20Handout.pdf
http://www.poolhelp.com/handouts/oB_...%20Handout.pdf
http://www.poolhelp.com/handouts/oB_...%20Handout.pdf
http://www.poolhelp.com/handouts/oB_...%20Handout.pdf
http://poolhelp.com/handouts/oB_Conf...%20Handout.pdf
http://www.poolhelp.com/handouts/oB_...%20Handout.pdf
http://www.poolhelp.com/npc_cal-poly.html
Ben I am a bit stunned by your comment and a little overwhelmed by all the attached content. I have perused the attachments you provided and am struck that there may not be a "good" solution to this problem, if it is plaster mottling, other than re-plastering. Is my inference correct?
Regarding the pictures the color of the stains on the steps and the swimout (photos 3 & 4) are better depictions of the actual color of the bottom stains, which are influenced by the depth of the water through which they are photographed.
This problem became pronounced about a week after I put a copper algaecide in the pool. It was 1 quart containing 13% of a copper compound. This would have introduced about 3 ppm of copper in a 20k gal. pool I think. I have paused to wonder if that's enough copper to stain/mottle the entire pool to one degree or another.
Thank you for considering my problem.
Plaster mottling is usually an appearance problem, not a function problem. Whether that means resurfacing or not is up to you.
However, a lot of plasterers don't guarantee mottling won't happen. And there's a LOT of debate about why it occurs (workmanship vs materials vs pool chemistry).
Copper may generate blue, blue-green, or even black stains . . . but not brown.
You can try putting Vitamin C on the discolored areas, as well is Iron Out. If it's copper, one of those will lift it off.