Over the last couple of years, I've had a large amount of leaves enter my pool over the fall and winter, then sit until spring. Last summer, I noticed the liner had taken on a distinct greenish stain. I first assumed algae, but setting a chlorine tablet against it provided zero results. A vitamin C tablet quickly brightened the liner to a lovely crystal blue. So, I assume I have mineral or metal stains.
Last year, I reduced the chlorine to zero, dumped ascorbic acid in the pool and within hours the liner was perfect looking. However, the stain came back within a few days of restoring the chlorine and ph levels. I researched and found I needed a sequestrant.
This year, before the season started, I bought a couple of pounds of ascorbic acid and two quarts of Pro Team metal magic. My plan was to get the water cleaned up (remove leaves, chlorinate hard, and filter continuously), then drop the chlorine to zero, do the ascorbic acid, then the metal magic.
However, after hitting the pool hard with chlorine for a couple of days, I noticed that the liner had cleared up! When I checked, the pool was very acidic (6.8). Now I figured the acidity has cleared the stain, but that it would come back when I got the ph right, so I got the ph up to 7.2 and added the Metal Magic. I let the filter run continuously for a couple of days, then went back to a normal routine. I never noticed any clouding of the water, as I've read that others have seen after using Metal Magic.
The pool stayed clear for a couple of weeks, and then *boom*. Literally overnight, the stain came back.
So now I have no idea what to do. Ascorbic acid cleans the liner up beautifully, seemingly indicating metal or mineral stain, but the Metal Magic did squat to keep the stain away.
I have always used strips to check my chemistry. After reading this forum, I realize they aren't wonderful. I'll buy a reagent kit and post some numbers here after I get it.