I am getting some calcium staining at my waterfall. Prior to draining my pool to 30% I had a CH of 420. I got the CH down to 360, I guess my water must be pretty hard. After a couple of weeks the CH has returned to 420. All other parameters are within BBB parameters. I have only been using bleach with great results after adding borates (50ppm). I cannot think why the CH should be rising. I will test my tap water when I get home, that may be some of the cause. Maybe the summer temps have something to do with this.