Great, you're almost through!!!!! Now that you're holding at 15 for two nights, it's time to measure pH, and TA. While you're at it, go ahead and get a calcium reading too, just for a baseline. You can go ahead and change out the sand now. Once you put the new sand in(Note: START THE FILTER UP IN BACKWASH MODE TO RINSE ALL THE DUST OUT OF THE SAND BEFORE SWITCHING IT TO FILTER MODE--please forgive the yelling, but see my post in the "pool lessons learned the hard way" forum). then you can go ahead and add your stabilizer. You can get it at WalMart, Lowe's, Home Depot, or the pool store. It's also labeled sometimes as balancer, but the active ingredient will be cyanuric or isocyanuric acid. Note how much is needed according to the label to get your pool to about 20 ppm, then only add about 1/2 that amount either through the skimmer (but then you can't backwash for at least a week) or better yet, put it in an old tube sock and hang it in front of a return in your pool until it dissolves. Post your readings for pH and TA, and we'll help you get it finished.

Janet

Note: Since pH tends to read falsely high with Cl levels above 10 ppm, I'd let it drift down a little before testing for pH and TA...maybe to around 6-8 ppm