London water supply infrastructure

London's water supply infrastructure has developed over the centuries in line with the expansion of London. For much of London's history, private companies supplied fresh water to various parts of London from wells, the River Thames and in the three centuries after the construction in 1613 of the New River, the River Lea, which has springs that divert alongside Hertford at an elevation of 40 metres AOD. Further demand prompted new conduits and sources, particularly in the 150 years to 1900 as the Agricultural and Industrial Revolution caused a boom in London's population and housing.

A crisis point was reached in the mid 19th century with biology proving outbreaks of cholera and other disease arose from commercial extraction of water from the Tideway, where the city once had its main filter beds and purification buildings. The Metropolis Water Act 1852 allowed all water extractors three years to find wells or non-tidal sources. London's water businesses (known also as undertakings) nationalised as the Metropolitan Water Board and then re-privatised. The population of Greater London is currently supplied by four private companies: Thames Water, Affinity Water, Essex and Suffolk Water and Sutton and East Surrey Water.

Most of the four companies' non-tidal Thames and Lea sites have current works for supplying domestic drinking water, drawing on rainwater across the Thames Basin. They have been supplemented in the 21st century by a slightly costlier extraction process operated most in drier seasons from the Tideway at Beckton. Pipes of a total length of greater than 13,000 miles are under the city's streets and pumping stations, testing and access stations provide for a relatively consistent and uniform supply of water which is highly regulated by water regulations.

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