Wedeco reactors with a wiper sweep the outside of the quartz sleeve to remove the scale and film that attenuate UV-C before it reaches the water. A wiper that is worn or wiping unevenly shows as falling measured intensity on lamps that are themselves still good. This is the 48 mm wiper rubber — the elastomer element that bears on the sleeve. It is the fastest-wearing part of the wiper assembly and the one to renew first when wiping performance falls off. Wedeco was founded in Herford, Germany in 1976 and is now a Xylem brand.