Re: Copper Stains
An interesting update but before I start I have still not received the iron test kit. Did test again for copper with 10 drops, the recommended dose, zero copper registered (the first ppm measurement on the color scale is 0.125), then tried 20 drops zero, tried 30 drops zero, finally tied 40 drops zero ppm, so it seems no copper in solution.
I read this post where JasonLion you recommended applying phosphonic acid directly to the spot:
http://www.troublefreepool.com/copper-stains-t7834.html
So although I had just raised the sequestrant from 12 to the 20 ppm recommended for metal removal I added another 20 ppm in total to the spots where I could still view faint stains, 40 ppm in the pool in total. Well I left for the day and returned in the evening before sunset and the pool was quite cloudy. I forgot that adding that much sequestrant would affect the chlorine. This then was going to be a possible algae bloom. I raised the chlorine from FC 1 (possibly lower) to shock levels for a pH of 6.2, Alk of 20, CH 350, and CYA of 25 to 5.5 ppm FC, this equates to a HOCl (as ppm Cl2) of 0.330. I calculated this using the "PoolEquations" spreadsheet, as the shock level at these low readings is much lower than the FC/CYA chart. Then left it overnight with the pump running and the pool was clear in the morning.
But the interesting part was that the faint stains nearly disappeared, they were visible the evening before to even a casual observer. But in the morning if one knew where they were you could still just find them but to someone new to the pool there appears to be no staining at all. These observations were made in the shade in the early morning, in the sun no stains are visible. There are stains but they are very, very faint. Somehow the combination of high sequestrant "The Magenta Stuff" and FC at shock levels seems to have helped. The Sequestrant had moved down to 14 ppm in the morning, I raised it to 20 ppm, and the FC was 4.5. I will let the FC settle to between be 2.5 and 3.0, a HOCl (as ppm Cl2) of between 0.137 and 0.167.
Well progress is being made, it seems a higher concentration of FC and adding more than the recommended dosage of sequestrant is more effective at removing the stains. Why I do not know, can anyone explain? This albeit more expensively as one has to add more sequestrant and more FC to offset the effect, still cheaper than re-plastering.
I did read that tannin stains have iron in them and are much harder to remove than no-tannin iron stains. I definitely had tannin stains as years ago we had a large tree near the pool. And at that time 1994 to 2000 I knew nothing about sequestrants, etc.
I also read in that same post above that if one does have copper stains, Ascorbic acid will actually make them worse. How many times did I treat with AA I dread to think, maybe 10 plus.
Supposed to get the iron test kit tomorrow, our local pool store found one on the Big Island of Hawaii. Hopefully the chemicals will not be out of date and I can report back as to whether or not there is iron, in solution.