I'm not asking for help, rather just wanted to post these pictures I took yesterday. This is staining left after a serious acid wash in 2008 and an AA treatment in Fall 2009. Since the AA treatment I have kept sequestrates in the pool but mostly for iron staining from our dust/sand/silt. (Fill water has no iron)
The acid wash was after pool had been sitting for many months, over the winter and into the next summer because of leak taking the level down, frogs establishing a breeding pond, lots of calcium scale, organic and metal stains embedded in calcium scale. We didn't hit the copper stains any harder than we did for fear of too much damage in the aging plaster.
The stains are very, very slowly lightening, but it may take years for them to lighten enough for my eye.
Ionization had been used in pool for about 18 years, but the most staining (but not all) occurred when the pool sat, unfiltered, and no backwashing to dilute the copper, with Floatron still working away throwing copper in pool, for a few sunny winter months.
Note in first three pictures the line where most of the staining has occurred. Most easily seen in first picture, starting right below the bottom step. This was the water line level when pool was closed due to leak that I could not find. Prior to closing the pool in the fall 2007 pool was filtered 24/7 with pool cleaner running several hours a day. I kept water topped up all summer by almost continuous topping up with fresh water. Cost for water replacement, over the summer, >$1000.
There is virtually no staining were the water pooled while doing the acid wash. During acid wash "bowl" of acid water was neutralized several times and pumped out of pool. So there is a nice stain free "bowl" in deep end.
The iron mostly stains the calcium scale and it is harder to release from the scale but hardly stains the plaster.
The copper hardly stains the calcium scale. It mostly stains the plaster that is free of calcium scale.
Iron staining is relatively easy to remove, via AA treatment. Copper stain could possibly be for the life of the plaster. When we did the acid wash we didn't get all of the calcium scale off of some areas for fear of too much damage to the plaster. BUT, by keeping the pH always below 7.5 and adequate use of the sequestrate 1) no more iron staining, 2) copper appears to be slowly releasing, 3) Calcium scale is slowly releasing.