Trying to figure out if I should replace the DE grids or the MPV on my 15 year old pool. Both are original parts, so admittedly they have outlived their expected life. I just cleaned the eight grids and have been able to balance the water for the most part. However, after I backwash and return to filter, DE and small dirt particles (small pieces of leaves, for example)come back through the jets for around two minutes or so. I don't have reason to think the MPV isn't working properly, but my pool guy suggested replacing. Thanks!