American Plumber, of Sheboygan, Wis., has made it simpler for plumbers to help its customers take control of their water quality with filters that easily twist into place. The DW-600 Under-Sink Drinking Water Filter System and WIC-600 Icemaker Filter System products are designed for easy, no-mess filter changes. Changing the filter on ice-makers and under-sink units used to be messy and difficult. Now, with two simple twists of the wrist, the old filter comes off and the new filter locks in.