London's water supply infrastructure has developed over the centuries in line with the expansion of London.

Beginning in the 16th century, private companies supplied fresh water to parts of London from wells and the River Thames. The New River Company pioneered the commercial supply of drinking water, extracting from the River Lea and distributing to customers' homes. Further demand prompted new sources, particularly when the Agricultural and Industrial Revolution caused a boom in London's population and industry.

A crisis point was reached in the mid 19th century with the discovery that cholera arose from the extraction of water from the increasingly polluted Thames. The Metropolis Water Act 1852 banned this practice, allowing water companies three years to find other sources, but issues with contaminated water persisted. In 1904, London's water suppliers were taken into municipal ownership as the Metropolitan Water Board, which substantially upgraded the water infrastructure, building many new reservoirs. Ownership subsequently passed to the Thames Water Authority, before being re-privatised in the 1980s.

Today, the population of Greater London is supplied by four private companies: Thames Water (76% of population), Affinity Water (14%), Essex and Suffolk Water (6.6%) and SES Water (3.7%). The London area is classified as "seriously water stressed", receiving less rain than Rome, Dallas, or Sydney, and continued investment will be required to counteract the effects of climate change and a growing population in the 21st century.

Most of London's water is now supplied from five large water treatment works fed from the Thames and Lea, and to a lesser extent from aquifers and a desalination plant at Beckton. Thames Water's London zone, which serves the majority of London's water users, has the capacity to supply of water per day.

Early London water supply

Through to the late 16th century, London citizens turned to the tidal Thames for much of their non-drinking water. For drinking, due to the brackish and perceptibly poor taste of the Thames, they tended to rely on wells and tributaries rising in around a dozen natural springs on the north side of the Thames, restricting the city's expansion south of the river.

In 1247 work began on the Great Conduit from the spring at Tyburn. This was a lead pipe which led via Charing Cross, Strand, Fleet Street and Ludgate to a large cistern or tank in Cheapside. The city authorities appointed "keepers of the conduits" who controlled access so that users such as brewers, cooks and fishmongers would pay for the water they used. Wealthy Londoners living near the conduits could obtain permission for a connection to their homes, but this did not prevent their unauthorised tapping. Otherwise – particularly for homes which could not take a gravity feed – water from the conduits was taken to homes by water carriers, often called cobs, a term seen as dated by the 18th century. Records of frequent drownings prove many poorer citizens needed or desired water from the Thames and the larger tributaries; quite large quantities were needed for iron-smithery, cooking and brewing for instance. The Great Conduit system was extended over time, and in the 15th century sources were increased, firstly by a conduit from Westbourne springs at Paddington, and secondly by another from the upper Fleet at Highgate which supplied Cripplegate.

Sixteenth century In 1582, Dutchman Peter Morice, supported by the City of London, developed one of the first pumped water supply systems for the city, powered by undershot waterwheels housed in the northernmost arches of London Bridge, which eventually came to be known as the London Bridge Waterworks. A series of pipes and cisterns distributed the water across the city. The supply from the waterwheels was not constant, so the water mains were switched on periodically, on a weekly schedule.

Around 1593, another pumping station was built, again with the backing of the city, at Broken Wharf on Upper Thames Street by Bevis Bulmer. Powered by four horses, the Broken Wharf Waterworks supplied Cheapside and a number of private households. While not a financial success, the waterworks continued to operate as a small independent company until it was purchased by the London Bridge Waterworks in the early 18th century.

Seventeenth century

The New River

The early seventeenth century brought the construction of the New River, a artificial waterway which still carries water into London from Hertford, where it is fed from the River Lea and several nearby springs.

Initially proposed in 1602 by Edmund Colthurst, who had obtained a patent from King James I granting him the water rights, approximately of channel were dug before the project ran into financial difficulties. In 1606, the City of London petitioned Parliament, which passed a series of acts overriding Colthurst's patent and transferred the water rights to Hugh Myddelton, who helped fund the project. Construction of the New River resumed in 1609 and it was officially opened in 1613.

The New River cost Myddelton a lot of money, but in 1612 he was successful in securing investment and assistance from the king. At completion, the New River had cost around £ (equivalent to £ in ), and by 1620, the total expenses for the first fifteen years had reached £ (equivalent to £ in ).

The New River Company, incorporated in 1619 as one of England's first joint-stock companies, took over the New River and became an important force in London's water supply until the company was absorbed by the Metropolitan Water Board nearly 300 years later.

The Great Fire

The construction of much of London's current water distribution infrastructure dates to after the Great Fire of London in 1666, which destroyed much of the city's previous wooden and lead water piping. The London Bridge Waterworks machinery was largely destroyed, but replacements engineered by Peter Morice's grandson remained under the bridge until the early 19th century, before the New London Bridge was erected in the 1830s.

New companies In the second half of the century, several new water works were established:

In 1669, the Shadwell Water Works were established by Thomas Neale as part of a larger project to develop the land at Shadwell. The works drew water from the Thames using a pump powered by four horses, and later by steam engines. It was incorporated by the Shadwell Waterworks Act 1691 (3 Will. & Mar. c. 37 ) in 1692. In 1673, the Millbank Waterworks was established by Michael Arnold, a brewer in Westminster, along with two co-owners. In 1675, a royal patent was granted to Ralph Bucknall and Ralph Wayne of the York Buildings Company to construct a horse-powered water works on the site of the York House estate, by the Thames south of the Strand. In 1692, the Hampstead Waterworks were incorporated as a joint-stock company, which was granted the rights to water from Hampstead.

Eighteenth century

The Chelsea Waterworks Company was established in 1723 "for the better supplying the City and Liberties of Westminster and parts adjacent with water".The London Encyclopaedia, Ben Weinreb & Christopher Hibbert, Macmillan, 1995, The company received a royal charter on 8 March 1723.Royal Charters, Privy Council website The company dug large water beds in borderlands of Chelsea with south-west Westminster (Pimlico) using water from the tidal Thames. In 1727 they purchased the Millbank Waterworks. Two Newcomen engine houses were erected in 1742 and 1746, and the first Boulton and Watt engine for water supply was installed on the same site in 1778.

Waterworks were established in East London, at West Ham in 1743 and at Lea Bridge before 1767.

The Borough Waterworks Company was formed in 1770, originally supplying water to a brewery and the surrounds: between London and Southwark Bridges. An adjacent zone was supplied by the London Bridge Waterworks Company.

The Lambeth Waterworks Company was founded in 1785 to supply water to south and west London. It was established on the south bank of the River Thames close to the present site of Hungerford Bridge where the Royal Festival Hall now stands. The first water intake of the company was on the south side of the river drawing on it around high tide. After complaints that the water was foul, the intake was moved to the middle of the river.

Nineteenth century

New companies

As the metropolis grew in the 19th century, London became the laboratory for water supply, and later waste removal. Several new water supply companies were established leading to a total of nine private water companies:

The South London Waterworks Company was established by a local act of Parliament, the South London Waterworks Act 1805 (45 Geo. 3. c. cxix). The company extracted water from the Thames beside Vauxhall Bridge. The West Middlesex Waterworks Company was founded in 1806 to supply water for Marylebone and Paddington. In 1808 the company installed cast iron pipes to supply water from its intakes at Hammersmith. The East London Waterworks Company, also founded in 1806, acquired the Shadwell Water Works, as well as works at Lea Bridge and West Ham on the Lea. The was incorporated in 1809 to supply Deptford, Lee, Greenwich, Lewisham, and Rotherhithe with water from the River Ravensbourne. The Grand Junction Waterworks Company was formed in 1811 to exploit a clause in the Grand Junction Canal Company's Act which allowed them to supply water via the canal from the Colne and the River Brent. It was thought these sources would be better than those of the Tideway, but they proved to be of poor quality and insufficient to meet demand, so the company resorted to taking from the Tideway south of Chelsea Hospital.

The Lambeth Waterworks Company expanded in 1802 to supply Kennington and about this time replaced its wooden pipes with iron ones.

Although the acts of Parliament which created the water companies encouraged them to compete for customers, the companies quickly realised that this would not be profitable. In 1815 the East London company agreed with the New River Company to set a boundary between the two companies' areas. In 1817, a similar agreement was reached between the New River, Chelsea, West Middlesex, and Grand Junction companies.

The London Bridge Waterworks Company was dissolved in 1822, and its water supply licence was purchased by the New River Company. Later that year, the Borough Waterworks Company purchased the London Bridge licence from the New River Company, and it was renamed the Southwark Water Company. The company extracted water from the Tideway using steam engines to pump it to a cistern at the top of a tower.

Slow sand filtration

In January 1829, amongst increasing complaints about the quality of water supplied by the water companies, the Chelsea Waterworks began using a pioneering new technology to purify its water. Originally developed by John Gibb of Paisley, Scotland, and deployed for the Chelsea Waterworks by James Simpson, the slow sand filter harnesses a complex biological film formed on the sand to provide excellent filtration of water with very little energy use. Filtration of water would eventually be mandated by the Metropolis Water Act 1852, and to this day a large amount of London's water is still purified using slow sand filtration.

Expansion

The West Middlesex Waterworks Company established a reservoir at Campden Hill near Notting Hill. In 1825 the company built a new reservoir at Barrow Hill next to Primrose Hill in North London.

In 1832 the Lambeth Waterworks Company built a reservoir at Streatham Hill, and in 1834 obtained an Act of Parliament to extend its supplied zone. In the same year, the Company brought of land in Brixton where it built a reservoir and works on Brixton Hill, by Brixton Prison.