Plaster stains keep coming back

[flavia]

Hi, I re-plastered my pool 3 years ago right before I closed the pool for the winter (I live in the Northeast). Upon opening the pool in April, the pool was severely stained. The plaster contractor attributed the stains to the heavy foliage nearby my pool (which had never stained before!) and offered me a free acid wash (in a brand new plaster!). The acid wash removed the stains but by the end of the season, different (and large) stains were back. I tried weekly dosage of Conquest/metal out, triple shocking and brushing, to no avail. New large stains kept reappearing and, upon calling the contractor again, he now wants me to have my water tested at a pool store. I keep the water perfectly balanced. I'm wondering if it could be iron or copper fittings that could be leeching into the pool and might have stained the floor in an week that I failed to add a sequestering agent. I'm ready to acid wash it again but wonder if it's metal or some problem with the plaster (can't figure out how to post pictures but I have them!). Thanks in advance!

[Teapot]

Metal out is bullshit, it's just a sequestering agent that hides the metals for a while. They shouldn't be allowed to call products such names. Extra oxidiser (triple shocking) will re oxidise the metals to any surface with a pH of 8+ although your pool water maybe pH 7.2 the fresh surface could well be higher. Testing the water once staining has happened often doesn't show the metals. Putting the metals back into solution with ascorbic acid you may then get a test result but ascorbic acid is not compatible with chlorine. You need zero chlorine to carry out the ascorbic acid treatment. The removal of metals is not an exact science, iron is not to tricky but copper if found is difficult so a water change is easier. After your acid wash did you add a high level of bicarbonate of soda to reharden the surface?

[flaviak]

Thanks, Teapot! No, after that acid wash I just refilled and rebalanced as usual. I bought acid ascorbic today and I'm gonna let the chlorine fully evaporate and go to zero and try the acid ascorbic treatment one more time before I give in and acid wash. I had tried acid ascorbic before but didn't pay attention to chlorine levels back then. Perhaps that's why it didn't work. Crossing fingers that it will work this time!