I'm still a newbie dealing with my first SLAMing as we speak. As a side, my CH is measuring at 900 with my speed stir. My tap water is measuring 350-375. This part of Texas is known for its hard water, so it's just something I've always lived with, but can my pool handle it? Does the CH really mean anything in of itself, or is the CSI what really matters? In the middle of my SLAM, my CSI is -0.06 according to PoolMath, so well within the acceptable range. But my worry is when the SLAM is done and I am maintaining the pool on a day-to-day basis.