I have the pleasure of having a nearly 800 foot dry well so have set up a cistern system. I pre-filter water thru a stainless steel filter box with a washable furnace filter. The filter still allows too much foreign matter in the tank. Adding gutter helmets has helped some but I need to add a roof washer that throws away the first however many gallons of water with most of foreign material. One was shown on recent This Old House Hour but I can't find info on website. It looked to be made from PVC. I need a source to purchase or plans on how to build.