<P> The Metropolitan Water Board and other local Water Boards were later combined into the Thames Water Authority, which was later privatized as Thames Water, a state - regulated private company which currently provides London's water supply . </P> <P> Greater London is currently supplied by four companies: Thames Water (76% of population), Affinity Water (14%), Essex and Suffolk Water (6.6%) and Sutton and East Surrey Water (3.7%). </P> <P> Most of London's water comes from non-tidal parts of the Thames and Lea, with the remainder being abstracted from underground sources . </P> <P> Much of the water piping in London is still cast iron piping which dates back to the nineteenth century and is slowly deteriorating . This has led to widespread criticism of Thames Water for the amount of water lost to leaks in its distribution network . As of 2007, Thames Water is still in the process of a rolling programme of upgrading the water supply network to use modern plastic piping . </P>

Where does the tap water in london come from