I followed the Ascorbic Acid method for removing the staining in my pool, particularly on the steps and the skimmers. Everything cleaned up and was doing great. I was able to keep chlorine around the 3-5ppm target value for my pool and keep pH no higher than 7.2 for about 1.5 weeks. Last week was really hot here (103-109) most days, so had to supplement my SWG (currently at 100%) to keep chlorine at that level. I noticed the staining starting to reappear on Friday and today it's definitely worse. I checked pH and it had creeped back up to 7.4, so I lowered it back down. Chlorine has been as high as 8ppm, but no higher with all the sun. So far, I've added a total of 4 bottles of The Purple Stuff since starting and 4 lbs of Ascorbic Acid.
What am I doing wrong? Do I need to do another treatment? Is there any way I can keep the staining gone permanently? Help!!! It was looking so good and now I'm back to square 1. We are expecting nothing but sun and 90 degree days this week also and I'm concerned about losing control to algae. Any suggestions would be appreciated!