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 and reservoirs 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  are under the city's streets. These are supported by pumping, testing and access stations and together provide for a relatively consistent and uniform supply of water which is highly regulated by water regulations.

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, organic-rich taste of that estuarine source they tended to rely on wells and tributaries rising in around a dozen natural springs on the north side of the Thames. This explains why the city spread scarcely in this, the medieval era, onto the other bank. 

In 1247 work began 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. Bathing places were also used at certain times, among certain people. The Grand Conduit system was extended over time. In the 15th century sources were increased, firstly by a conduit from Westbourne springs at Paddington, secondly by another from the upper Fleet at Highgate which supplied Cripplegate.

Sixteenth century
In 1582, Dutchman Peter Morice (died 1588) developed one of the first pumped water supply systems for the city, powered by undershot waterwheels housed in the northernmost arches of London Bridge spanning the River Thames. The machinery was largely destroyed in the Great Fire of London in 1666 but replacements engineered by his grandson remained under the bridge until the early 19th century, before the New London Bridge was erected in the 1830s.

Seventeenth century 

Hugh Myddleton was the driving force behind the construction of the New River, the engineering project that brought fresh water from Hertford, Hertfordshire to 17th century London. After the initial project encountered financial difficulties, Myddleton helped fund the project through to completion. The New River was constructed between 1609 and 1613 (being officially opened on 29 September that year), 38 miles (60 km) long.  It starts at an elevation of 40 metres. It was not initially a financial success, and cost Myddleton substantial sums, although in 1612 he was successful in securing monetary assistance from King James I.  The New River Company became one of the largest private water companies, supplying the City of London and other central areas.

The construction of London's current water distribution infrastructure dates back to the Great Fire of London in 1666, which destroyed most of the city's previous water infrastructure, most of which was made of wood and lead. One waterworks not affected by the fire was at Shadwell by the Thames which dated from 1660.
The city's water supply and distribution infrastructure has been continuously updated and upgraded since then.

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 company received a royal charter on 8 March 1723. The company dug large water beds in borderlands of Chelsea with south-west Westminster (Pimlico) using water from the tidal Thames.

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 London spread in the 19th century, new facilities were needed to serve the increasing population in newly developed areas. Several new water supply companies were established leading to a maximal time of nine private water companies, each with a local monopoly.

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

The South London Waterworks Company was established by private act of parliament in 1805. Similarly 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 (eventually these became the north half of the City of Westminster. In 1808 the company installed cast iron pipes to supply water from its intakes at Hammersmith.

The East London Waterworks Company was founded by Act of Parliament in 1806, acquiring existing waterworks at Shadwell on the Thames, Lea Bridge and West Ham on the Lea.

The Grand Junction Waterworks Company 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/or the River Brent namely the Brent Reservoir. It was thought these sources would be better than those of the Tideway, but they proved of poor quality and insufficient to meet demand. After trying to resolve the problems the company resorted to taking from the Tideway south of Chelsea Hospital.

Expansion

Statutes that established the London water companies weakly intended they would compete for customers. In 1815 the East London company drew up the first defiant legal agreement. This was with the New River Company defining their respective areas supplied.

The London Bridge Waterworks Company was dissolved in 1822, and its water supply licence was purchased by the New River Company. Later that same 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.

The West Middlesex Waterworks Company established a 3.5 million gallon 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 1825, the ponds of the Chelsea Waterwork Company were used as the basis of the Grosvenor Canal which was opened to traffic that year. By this time there were complaints about the quality of the water that the company was drawing from the River Thames, and in 1829, under engineer James Simpson the Chelsea Waterworks Company became the first in the country to install a slow sand filtration system to purify the water.

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.

In 1833 the South London Waterworks Company was supplying 12,046 houses with approximately 12,000 gallons of water per day. In 1834, the company was renamed the Vauxhall Water Company.

The Grand Junction Waterworks Company built a pumping station near Kew Bridge at Brentford in 1838 to house its new steam pump and two similar pumps bought from Boulton, Watt and Company in 1820. The water was taken from the middle of the river and pumped into filtering reservoirs and to a  tower to provide gravity-fed water. A six to seven mile (11 km) main took the water to a reservoir on Campden Hill near Notting Hill with capacity: 6 million gallons.

In 1829, the East London Waterworks Company moved their source of water further up river to Lea Bridge as a result of pollution caused by population growth. Clean water was now abstracted from the natural channel which had been by-passed by the Hackney Cut, to a new reservoir at Old Ford. In 1830 the company gained a lease on the existing reservoir at Clapton. In 1841 the East London Waterworks Company was supplying 36,916 houses. In 1845 the limits of supply of the company were "all those portions of the Metropolis, and its suburbs, which lie to the east of the city, Shoreditch, the Kingsland Road, and Dalston; extending their mains even across the river Lea into Essex, as far as West Ham." The water supplied by the company was taken from the Lea, with waterworks on  of land at Old Ford.

The Lonsdale Road Reservoir (also the Leg of Mutton Reservoir or Leg o' Mutton Reservoir) was built in 1838 and decommissioned in 1960, it is now a local nature reserve.

On 10 January 1845 the Southwark and Vauxhall Waterworks Companies submitted a memorandum to the Health of Towns Commissioners proposing amalgamation. A consequent bill was passed by parliament, and the Southwark and Vauxhall Waterworks Company was formed later that year. The area supplied by the SVWC was centred on the Borough of Southwark. Thus it spread east to Rotherhithe, south to Camberwell. It also spread west including Battersea and parts of Clapham and Lambeth.  The amalgamated company established waterworks at Battersea Fields with two depositing reservoirs with a capacity of 32 million gallons; and two filtering reservoirs holding 11 million. In 1850 the company's "treated" water was described by microbiologist Arthur Hassall as "the most disgusting which I have ever examined". His tests and those of others precipitated the law of two years later.

Metropolis Water Act

The companies often supplied too little water.  It was often contaminated.  The extent of contamination was confirmed by John Snow during the 1854 cholera epidemic. Population growth in London had been very rapid (more than doubling between 1800 and 1850), with little increase in infrastructure. The Metropolis Water Act 1852 was passed to "make provision for securing the supply to the Metropolis of pure and wholesome water." Under it, it became unlawful for any water company to extract water for domestic use from the tidal reaches of the Thames after 31 August 1855, and from the end of that year all such water was required to be "effectually filtered". The Metropolitan Commission of Sewers was formed.  New water intakes, plants and pumps would have to be west of where the river became tidal (Teddington Lock) and along the Lea.

The Chelsea Waterworks and the Lambeth Waterworks companies, who shared the services of James Simpson, established the reservoirs and filtration plants at Seething Wells on the riverside, spanning Long Ditton and Surbiton. The Chelsea's former central site was taken over by railway companies for Victoria Station and its goods sidings and yards. The Grand Junction, West Middlesex and Southwark and Vauxhall Waterworks Companies built the works above Molesey Lock at Hampton designed by Joseph Quick. Though small, the Grand Junction and Sunnyside Reservoirs there were supplemented by filter beds – all by the SVWC in 1855. These served a  diameter main ending at Battersea. A third reservoir was opened later that year between Nunhead Cemetery and Peckham Rye. 

In the mid 19th century the East London Waterworks Company purchased the Coppermill at Walthamstow and modified it to drive a water pump to assist in the building of reservoirs on nearby marshland in the Lea Valley . The company built a series of reservoirs which were High Maynard Reservoir, Low Maynard Reservoir, five linked numbered reservoirs making the Walthamstow Reservoirs, the East Warwick Reservoir and the West Warwick Reservoir.

In 1872 the Lambeth Waterworks Company moved upstream on the Thames to Molesey, followed by the Chelsea Waterworks Company. They built the Molesey Reservoirs there in 1872.

The East London Waterworks Company replaced their reservoir at Clapton with one at Stamford Hill in 1891; places which adjoin in today's London Borough of Hackney.

In 1897 the New River Company started developing the Kempton Park works (today all in Hanworth). This would supply more water than the plant at Cricklewood that drew on the River Brent.

In 1898 the SVWC started work on the Bessborough and Knight Reservoirs across the Thames from Hampton at Molesey. By 1903 the SVWC supplied a population of 860,173 in 128,871 houses of which 122,728 (95.3%) had a constant supply. The Lambeth Waterworks company started work on Island Barn Reservoir at Molesey in 1900.

Twentieth century 

The private water companies were nationalised, by compulsory purchase, from 1902–03. The Metropolis Water Act 1902 (2 Edw.7, c.41) created the Metropolitan Water Board ("MWB"). It was founded in 1903 and incepted in the Act with 67 members; 65 of these nominees of local authorities, who then appointed the paid Chairman and Vice-Chairman.  The Staines Reservoirs Joint Committee and these companies were included:
 The New River Company
 The East London Waterworks Company
 The Southwark and Vauxhall Waterworks Company
 The West Middlesex Waterworks Company
 The Lambeth Waterworks Company
 The Chelsea Waterworks Company
 The Grand Junction Waterworks Company
 The Kent Waterworks Company
Acquired at no cost were the water undertakings of Tottenham and Enfield Urban District Councils.  

Supply pipes stretch a similar distance to sewerage – 13,000 miles in Greater London alone.

The MWB opened the East London Waterworks reservoirs Banbury Reservoir in 1903, Lockwood Reservoir (1903), and the Bessborough Reservoir (1907), Knight Reservoir (1907) and Island Barn Reservoirs (1911) at Molesey. It opened the Kempton Park Reservoirs (including Stain Hill Reservoirs) in around 1907.

In 1902, the extraction pumphouse opened at Hythe End for the Staines Reservoirs and Staines Reservoir Aqueduct. These supply water to the East London Waterworks within the north-east limits of Sunbury (returned to a field), "Kempton Park" Waterworks (north-east) and Hampton Advanced Water Treatment Works (south). The Thames Conservancy limited such taking (abstraction) especially in drought. Thus the large reservoirs ensured a few weeks' supply or longer with water restrictions.

River water improves in quality in the reservoir as solids settle and organic contaminants are adsorbed and degraded through a combination of natural biological processes aided by sunlight and oxygenation.  

The Metropolitan Water Board Railway was opened in 1916 to carry coal from the river at Hampton to Kempton Park. An engine house with powerful steam engines was opened at Kempton Park in 1929, which has now become Kempton Park Steam Engines museum.

The MWB opened reservoirs: the King George V (Lea Valley) in 1912, Queen Mary (Littleton) in 1925, King George VI (Stanwell Moor) in 1947, William Girling Reservoir (replacing Chingford and Edmonton Marshes, Lea Valley) in 1951, Queen Elizabeth II (Molesey) 1962, Wraysbury Reservoir 1967, and Queen Mother (Datchet) 1976.

The MWB built tunnels for piping of water across London. By the 1950s the flow of the Lea was less than the demand from the eastern areas, as west Essex's population swelled. The Thames–Lea water main (tunnel) piped water from the non-tidal Thames to reservoirs in the Lea Valley. It runs from Hampton water works to the Banbury and Lockwood reservoirs at Chingford. It is 19 miles (30.6 km) long, 2.6 metres in diameter, and below ground by  to . It has twenty-two 12-foot-across access shafts. It was constructed by the consulting engineers Sir William Halcrow & Partners, 1955–59 for about £5,515,000, ). It transports up to 120 million gallons per day (6.3 m3/s).

The Metropolitan Water Board and other local Water Boards (the Thames Conservancy, the Lee Conservancy Catchment Board and parts of the Essex River Authority and parts of the Kent River Authority) were combined into the Thames Water Authority from 1 April 1974. This was under the provisions of the Water Act 1973 which was another step towards an integrated policy of water management. The Thames Water Authority was later privatized in 1989 as Thames Water, under the provisions of the Water Act 1989, as a state-regulated company that provides most of London's supply, as detailed below.

Present day 
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%).

Most of London's water comes from non-tidal parts of the Thames and Lea, with the remainder being abstracted from underground sources.

Reservoirs 
The following operational reservoirs (in 2020) supply water to London.

Water piping in London is mainly cast iron piping which dates back to the nineteenth century and suffers from rust and vibration; some was until the 2010s wood such as at Temple. This leads to criticism of the supplier for the volume of leaked water and associated street flooding by water mains. As of 2007 the supplier is in a decades-long scheme to install modern plastic piping.

In 21st-century infrastructure is the Thames Water Ring Main, the "backbone network" of London's water supply. This connects all the waterworks, and pumping stations. The century has seen a contingency treatment works built, mostly for droughts, at Beckton.

Water Treatment Works
The Water treatment works on the Ring Main are:
Ashford Common WTW
Kempton Park WTW
Walton Advanced WTW
Hampton WTW
Coppermills Lane WTW

Pumping stations
The pumping stations on the ring main are:

Surbiton PS
Merton PS
Streatham PS
Brixton PS
Battersea PS
Park Lane PS
Kew PS
Holland Park Avenue PS
 Barrow Hill PS
New River Head PS
Stoke Newington PS

Access
Hogsmill — Access
Raynes Park — Access
Mogden — Access

Storage

Honor Oak — Underground Storage
Barnes — balancing storage

See also 
 History of London
 List of reservoirs and dams in the United Kingdom
 Metropolitan Drinking Fountain and Cattle Trough Association
 Kew Bridge Steam Museum
 London sewer system
 History of water supply and sanitation
 Thames Water Desalination Plant

References

External links 
 History of Thames Water
 Is London water safe to drink?

London water infrastructure
Thames Water