Hello everyone. I have an above ground oval pool with a vinyl liner with a DE filter. I switched to the TFP method about 3 years ago. Prior to the TFP method, I was constantly fighting algae and shocking the pool with bags of shock from the pool store at least every week. Now that I've taken control of the pool, it's been mostly Trouble Free™. My question is regarding stains observed on my wedding cake stairs and on the liner itself. I noticed them last year but cleaning the stairs removed the stains. But now I see them again and I decided to see what the stains are. I tried the crushed vitamin C tablet and sure enough it removed the stains from the stairs (see pictures).
I also purchased the Taylor iron test kit and it showed 0 ppm in the pool water. I fill the pool water with municipal water which is sourced from surface water, so I wasn't expecting iron coming from that. I'm at a loss as to where I could get the iron stain, unless it's not really iron. The only odd thing I use that could be contributing are the drainage stones I put in the cylinder in the stair weight. I'm closing the pool on Saturday so I'll address the staining in the pool in the spring. I don't have a heater which could cause copper staining and I have borax in the water @ 50 ppm (if that's important).
Does anyone have any clues as to what I'm dealing with?
The stones look like this:
Stairs after vitamin C tablet