This is the first summer with my new pool. It's a 20x40 42000 gallon rectangle. It is an auto pilot salt water system with a large sand filter. I removed the cover after winter and it was a swamp. I worked with the local pool shop and got the green to go away and had the pool perfectly clear and sparkling. The water chemistry was "perfect". I recently had some maintenance done to the pool which required me to drain the water down around 8 inches. Since I refilled the water that I drained it has remained at zero chlorine. The other tested parts of my water are good. I currently have 60 CYA and added 8 lbs of Power Powder Plus. The water has remained cloudy with a slight green tint. I can't figure out what I need to do to get the FC where it needs to be. I read about slamming the pool, is this what I need to do? If so, where do I start?
Thanks in advance for any assistance.