If the filter is working properly no DE should get into the pool. If you're getting DE back into the pool it's coming from a tear in one of the grids/fingers (depending on your style filter), a crack in a manifold, or a tear in a gasket/o-ring. What model filter do you have?
It is a Pentair fns plus 36. Grids are new and there are no cracks in the manifold. Was thinking maybe the o-ring around the stack pipe in the filter was bad and maybe letting small amounts of de back into the pool. Thoughts?
It is possible there is a small hole in the fabric that is letting DE into the pool. Over time as the DE builds a layer on the outside of the grid, it should plug that hole preventing DE to enter the pool