The Story of London’s Sewer System

Hidden beneath the city streets of London lie 2,000 kilometres of brick tunnels that take raw sewage from our homes, along with 130 kilometres of interconnecting main sewers the size of railway tunnels.

Much was engineered in the middle of the 19th century, including magnificent cathedral-like sewage pumping stations.

The Great Stink

In the 19th century, London’s population numbered around 2 million. The city suffered fatal epidemics of cholera when thousands died. The Victorians had no known cure.

It was widely believed breathing in ‘miasma’, foul contaminated air, caused disease and death.

London-based physician Dr John Snow put forward the theory that the condition was water-borne, but his ideas received little attention. The year 1853-54 saw cholera claim a further 10,738 victims.

In the scorching summer of 1858, temperatures averaged 35 degrees Celcius. The stench from the Thames, the ‘Great Stink’, became overwhelming for those nearby, including Parliament, whose legislative business was disrupted.

Tons of lime were spread on the Thames foreshore and near the mouths of sewers discharging into the river to try and dissolve the toxic effluent, with little effect.

Parliament was forced to legislate to create a new unified sewage system for London. The Bill became law on 2 August 1858.

Sir Joseph Bazalgette

The Great Stink was the catalyst for radical change. Sir Joseph Bazalgette was the Victorian engineering mastermind and public health visionary behind the vast sewage system that Londoners still rely on today.

Before Bazalgette’s designs, raw sewage seeped from inadequate sewers into the River Thames, turning it into a stinking open sewer, its foreshore thick with untreated human waste, industrial discharge and slaughterhouse effluent.

The increasingly widespread use of the new flushing toilets exacerbated the problem, overwhelming cesspits and causing more waste to flow into the river.

Bazalgette was chief engineer of the Metropolitan Board of Works (MBW), having begun his career in public health engineering in 1849.

He spent several frustrating years drawing up plans for a revolutionary rethink of the city’s sewers, only to see them repeatedly shelved as Parliament and others argued about the system’s merits.

Parliament gave full responsibility for cleaning up the Thames to the MBW, favouring Bazalgette’s plans and the ability to borrow £3 million. This was a colossal sum then, which had more than doubled by the end of the project.

When completed in the mid-1870s, the new sewage network’s enclosed design, which captured sewage and rainwater, virtually eliminated cholera.

Dr John Snow’s theory about cholera being a water-borne disease was correct, although he died at the height of the Great Stink without knowing he had been vindicated.

Integral to Bazalgette’s plans was constructing four major pumping stations to lift sewage from low-lying sewers for discharge eastwards.

Beautiful Victorian pumping stations

The magnificent Crossness Pumping Station raised the effluent from the south of the river up 12 metres into a reservoir using four enormous powerful beam engines.

It was designed by James Watt & Co and named Victoria, Prince Consort, Albert Edward and Alexandra.

From here, it was released into the Thames well beyond London, swept out to sea on the ebbing tide.

Abbey Mills pumping station pumped effluent from the north of the river. Completed in 1868, it’s another temple of engineering in elaborate Italianate Gothic style, for similar discharge into the Thames, well beyond the city limits.

London’s embankments

Bazalgette, who remained Chief Engineer of the MBW for 33 years, also changed the face of London by reclaiming 7 kilometres of riverside land and muddy foreshore.

Here, he created the vast Albert (1869), Victoria (1870) and Chelsea (1874) Embankments to accommodate his low-lying sewers.

He also laid out new city thoroughfares, including Shaftesbury Avenue, Northumberland Avenue and Charing Cross Road, and built bridges across the Thames, including Hammersmith and Battersea.

Joseph Bazalgette’s enlightened public health legacy is largely unsung today, with his sewer network hidden deep beneath the city. This small wall-mounted bust is Bazalgette’s only public memorial.

Upgrading Bazalgette’s sewer system

London’s 150-year-old sewage system is today struggling under the strain of the city’s ever-increasing population, which is now nearly 9 million.

Millions of tons of raw sewage still spill untreated into the Thames each year, especially after extreme weather.

Tideway is building a ‘super sewer’, the Thames Tideway Tunnel, to relieve the pressure on the old system. It will run under London for 25 kilometres, from Acton in the west to Beckton in the east, at depths between 30 and 60 metres, using gravity to transfer the waste eastwards for treatment. It is due for completion in 2024.

As part of the super sewer project, a new barrier is planned for the river by Blackfriars Bridge. The public open space will be named Bazalgette Embankment in honour of Sir Joseph Bazalgette.

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Written by Nicky Hughes.

Further reading

Secret Worlds Hidden Beneath Surface Structures

Walking on History: Surprising Secrets of Manholes

How Human Faeces Can Preserve Plant Fossils