Hello everybody. Been lurking here for a couple of months. Implemented TFPC in October and the pool has never looked this good. Came across this site while searching for answers to what turned out to be a metal staining problem. Successfully resolved that with an ascorbic acid treatment. I coordinated that effort with some pool work that required draining, so the day after the stain cleared up, I was able to drain the water. When I refilled, I took off the SWG (as it had failed and needed replacement) and returned the pool to its original fresh water configuration, (I had already started using bleach when the SWG failed about a month earlier), and fully implemented the TFPC system. Up to now I've been able to find an answer to every single question that has come up by searching the site and forums, and there have been a lot, and I'm amazed at the wealth of information here, and very grateful... and feel validated in my general impressions of pool stores. My question about the TA spec is about the notation "TA 70-90+". What exactly does that plus sign mean? Thus far, I've been maintaining in the 70 to 90 range, but every time I look at that spec I wonder about it. Cheers!