The local pool store sold me a 20 pound bag of DE and told me to put 1/3 of it into my skimmer. So I did and my filter glogged right up. All day today we have had to pull out the filter and clean it every 40 mins or so because the return jets stop flowing. 1/3 of a bag is about 7 pounds. We have a 20,000 pool and the filter system is Hayward 120. Pool store says it was my fault for putting it in too quickly but their instructions were to pour some, let go down and pour more, which I feel I did.