United Utilities identified two major water treatment plants at the outset of the third Asset Management Plan (AMP3) investment period, these being Oswestry and Watchgate WTWs, that were in need of major investment to meet tightening water quality standards for trihalomethanes (THMs) and Cryptosporidium. The two works are at the head of extensive treated water aqueduct systems, namely the Haweswater and Vyrnwy Aqueduct systems. These aqueducts transport water to two large urban conurbations, Liverpool and Manchester, from treatment plants that are approximately 100 km from the start of the distribution network. As with most large cities the network system is both extensive and complex with a number of service reservoirs and points of secondary chlorination.