WAFER BUTTERFLY VALVES
Wafer butterfly valves are typically sandwiched between two flanges using bolts and nuts; the pressure of the nuts on the backside of the flange holds the valve in place. Wafer butterfly valves consist of a seal that fits around the wall of a pipe, a round disc, and a control lever. The wafer butterfly valves discs' rotates ninety degrees at the turn of the lever. When the disc is parallel to the flow of water, the valve is in open position and lets all liquids pass; when the handle is turned, the disc rotates around to a position parallel to the flow of water. In this closed position, the disc fits snugly into the seal and blocks all flow through the pipe.
Wafer butterfly valves can be made of a variety of materials, including stainless steel, plastic, and other metals.