I opened my pool this year after it having been closing it in August 2014. The water was green and filthy and after putting in chemical and running it since Wednesday it is blue but too cloudy to see the bottom. After backwashing and replacing the DE in my HAyward 2420 filter I noticed the DE going back into the pool. So far I have replaced three torn filter grids, as well as the multiport valve which was damaged. None of the O rings are missing or damaged, and I am not seeing bubbles in the filter. I let the filter run, backwashed when the pressure went up, but still had DE coming back into the pool when I went to replace it. I am at a loss as to what else could be the cause.