I have been vacuuming my Coleman 16' x 48" power steel pool about twice a week. I have a large maple next to the pool and get leaves, bugs, twigs and some dirt but yesterday evening I noticed a great deal of dirt on the bottom which was unusual. This morning I was vacuuming it out and remembered that a neighbor just across the street from our yard had a new roof put on their garage yesterday. Now all that dirt showing up makes sense.