I have read posts on this forum in the past that have been very helpful. After opening the pool a few weeks ago, I noticed DE on the bottom of the pool. I replaced the spider gasket on the multi-port valve that had been worn and thought that would correct the problem. I also replaced the grids and top manifold in the filter a few days ago and realized this morning, DE is still returning to the pool. So, I opened the filter and was inspecting it and noticed as the filter was open, the water drained out. There are no leaks on the outside of the filter and I am assuming the water returned to the pool. If the water is returning to the pool, I am sure the DE must be as well. Can someone tell me what would cause this problem and how I could correct this? I have owned and maintained my pool for the past eighteen years and have not experienced a problem like this. Any suggestions/recommendation would be greatly appreciated.