Approximately 5,000 square kilometres of the greater London area of South Western Ontario is supplied by two Water Treatment Systems:

The Lake Huron Primary Water Supply System services the communities of London, Lambton Shores, North Middlesex, South Huron, Bluewater, Middlesex Centre, Lucan-Biddulph and Strathroy-Caradoc from a water treatment plant located east of the village of Grand Bend in South Huron.  The plant has a current treatment capacity of 340 million litres per day (75 Million Imperial gallons per day) and serves a population of approximately 325,000 people.

The Elgin Area Primary Water Supply System services the communities of St. Thomas, London, Aylmer, Bayham, Central Elgin, Malahide and Southwold from a water treatment plant located east of the village of Port Stanley in Central Elgin.  The plant has a current treatment capacity of 90 million litres per day (20 million Imperial gallons per day) and serves a population of approximately 100,000 people.

HELP Clean Water is a regional project that will serve the needs of more than 500,000 people be implemented in phases over the next 20 years, at an estimated total cost of approximately $350 million.

Each of the Lake Huron Primary Water Supply System and Elgin Area Primary Water Supply System have implemented an Environmental Management System registered to the ISO14001:2004 international standard.