I am new this summer to the Trouble Free Method, so I am still learning. With that said, I'm not sure if I should SLAM or not... I am losing chlorine overnight - last night was 2ppm. The water looks clear but there is a gray 'powdery' looking material on the bottom - even after vacuuming yesterday. One other factor changed in the past week. My sand filter started making a 'crackling' sound - like air is in it. I talked to pool store and they said the sand needs changed. Could the gray powdery material be something the filter is pushing back in and that is eating up the chlorine? Should I get filter sand changed before SLAMing? Thank you for any advice!