I have written this as part of my rewrite of Michells Construction, I has taken the best part of a week to review a lot of small notes I have made in my Knowledge Bank within Apple Notes, and pull this article together.
No Technologist / Technician or Architect Surveyor, can get way with not having to deal with drainage, whether it is a completely new system, or as most often, the connection of a new system to an older pipe network, single pipe or twin, storm and Foul
As always this article is meant to be a catalyst for a lot of further reading, perhaps a few visits to the London pumping stations, and certainly Paris to see the excellent museam on the banks of the Seine.
I came though College with Peter Burberry’s excellent book Environment & Services, sadly its last update was 1997, but reading it though, I thought how well its lasted, and certainly worthy of any ones library. My own copy both the 1970 and 1997 versions are littered with sticky notes and update suggestions. Sadly I think Peter passed away in early 2000”s certainly his book is now in need of an update.
#article#Sewer#drainage#SUDS #Climate-Change
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Drainage & Plumbing
Drainage design is the use of carefully crafted rules that have evolved from the trial and so often error of installations all over the world, for the correct size shape and fall, together with the adequate quantity of water needed to carry the solids of varying type, and shape from your building to any number of Sewage plants dotted round all our cities.
In early Victorian buildings, the means to remove human waste was done via the use of a chamber pot, often thrown out of a window into the street below, to be washed away by the next rain fall. As you can imagine this was not an ideal situation. Big cities were extremely smelly, and disease was rife due to all the excrement and other items lying in the roadway and if there were any, gutters.
To understand sewage, we need to understand the term used, Sewage is the liquid with partial solid matters suspended within water, and as you will learn later in the rules that were eventually adopted, the size, shape and volume of water is a huge part of the design of any sewer, together with the speed at which it flows, induced by the fall of the pipe or gutter, were so often a experiment, many of which failed.
So often water for drinking and cooking was taken from wells, as cities grew so did the number of wells, all surrounded by streets, full of the effluents for some times weeks without rain to flush it way to local streams. It does not take a lot of imagination to realise that a lot of this soaked down through the soil into the very wells being used to provide water.
Gutters included at the sides of roads, were therefore installed not just to channel rainwater but also to ease the removal of all the effluent, both solid and liquid. Often the gutters were covered or fed into a pipe, to crossroad junctions or pedestrian areas, the sewer was born.
But the sewage needed to go somewhere, this was often the local stream or a man made cesspit, often a hole dug in the ground.
It comes as no surprise that many cites were hit by massive outbreaks of many diseases. A massive outbreak that spread through London at this stage was a a major turning point forcing change. That great disease that significantly impacted London and ultimately forced major change in its sanitation system, leading to the development of the modern sewer network, was Cholera.
While there were several significant cholera outbreaks in the early-to-mid Victorian period (e.g., 1831-32, 1848-49), the one most famously associated with a crucial discovery and eventually driving change was located in London, the 1854 Broad Street Cholera
Outbreak in Soho, London.
* The Disease: Cholera, a waterborne disease, killed thousands.
* The Key Event: In the 1854 outbreak, a physician named Dr. John Snow conducted a pioneering study. He mapped the cases and identified the source as a single contaminated public water pump on Broad Street (now Broadwick Street), proving that the disease was spread through water contaminated with sewage, not “miasma” (bad air), as was widely believed at the time. He famously convinced local authorities to remove the pump handle, which effectively ended the local epidemic.
* The Catalyst for Massive Change: While Dr. Snow’s discovery was hugely important, it took a more immediate crisis to spur Parliament into action for a full-scale public works project.
* The Metropolitan Buildings Act (1844) This Act was one of the earliest to set a clear, mandatory standard for new construction. It specified that all new buildings had to be connected to a sewer, not a cesspool.
The Metropolitan Commission of Sewers Act (1848)
* The Body: This Act established the Metropolitan Commission of Sewers (MCS), which, for the first time, consolidated the control of London’s sewage infrastructure under a single authority (previously, there were multiple, uncoordinated local commissions).
* The Crucial Mandate: The MCS was given the power to legally enforce two devastatingly consequential bylaws:
* It required all new houses to have a water closet (WC).
* It gave the Commissioners the authority to order the abolition of existing cesspools and mandate that all existing houses connect their drains directly to the public sewer network.
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The Immediate, Disastrous Consequence
While the intent of these laws was to improve public health, the effect was initially the opposite, creating the very problem Bazalgette would later solve:
* System Overload: The old sewers were primarily designed to handle rainwater and surface runoff, not the daily output of hundreds of thousands of water closets. The widespread adoption of flushing toilets (popularized after the Great Exhibition of 1851) suddenly channelled massive volumes of liquid human waste into the narrow, unsuited sewers. many of which drained into the Thames. The designs from people like Thomas Crapper, became almost a status symbol.
* The Thames Becomes an Open Sewer: Since the existing sewers simply ran downhill to the nearest open river or stream, and eventually all discharged directly into the River Thames, the new laws effectively turned London’s main waterway into one giant, concentrated, effervescent sewer.
* This was the “Great Stink” of 1858. A scorching hot summer exacerbated the stench of the River Thames, which was essentially a vast open sewer, causing Parliament (located right by the river) to be overwhelmed.
The London Method of Pumping
This “Great Stink,” combined with the repeated cholera outbreaks, finally provided the political will and funding to approve the immense project designed by engineer Sir Joseph Bazalgette—the construction of London’s comprehensive, large-scale, covered sewer system, which began in 1859.
This massive surge of raw sewage directly into the tidal Thames made the water lethal (as proven by Dr. John Snow in 1854) and created the horrific conditions that culminated in the Great Stink of 1858, which finally forced Parliament to commission Bazalgette’s complete redesign.
Bazalgetts solution for London was a system of six main intercepting sewers (three north of the Thames, three south) that ran parallel to the river. These were built with a minimum, continuous, and precise gradient (fall) to use gravity to carry waste eastward, far past the city. Where the land was too low, he designed magnificent pumping stations (like Crossness and Abbey Mills) to lift the sewage into the higher-level outfall sewers so that gravity could continue the journey.
Bazalgett also designed the Egg Shaped Sewer, The design was a direct, practical solution to the most pressing problem of early sewer attempts: stagnation and blockage.
1. The Design Principle: Self-Cleansing
Older sewers often had flat or rectangular bottoms. When the volume of waste (the “flow”) was low—which was most of the time—the sewage spread out into a thin sheet. This slow flow allowed heavy solids to settle and putrefy, releasing foul-smelling and disease-carrying gases (the dreaded “miasma”).
The egg-shaped sewer, designed by Bazalgette, is built with its narrow, rounded end at the bottom and its wider, curved section at the top.
2. How it Works: The Scouring Effect
* Concentrated Flow: By narrowing the channel at the base, the design forces a low volume of liquid waste to be concentrated into a smaller, deeper column.
* Increased Velocity: This concentration of mass within a smaller space naturally increases the speed (velocity)of the flow.
* Self-Cleansing (Scouring): This higher velocity creates a powerful scouring or cleansing action along the curved base, ensuring that solid matter (like “night soil” and debris) is continually swept along the pipe and prevented from settling and causing blockages.
3. Dual-Purpose Shape
The egg shape is functionally superior for two reasons:
* Low Flow Efficiency: The narrow bottom ensures that even a small amount of waste can achieve the necessary velocity for self-cleansing.
High Flow Capacity: The wide top provides a large capacity during periods of high flow, such as heavy rainfall, allowing it to handle combined sewage (foul water) and stormwater without overflowing.
This elegant geometric solution was a key factor in the long-term success of Bazalgette’s system, allowing his brick tunnels to function reliably for over 150 years.
Other large cites were also just as bad, but thier method for dealing with the problem were slightly different, Birmingingham, my home city, developed a The sanitary systems of Paris and London, both transformed in the mid-19th century, offer a fascinating contrast in engineering philosophies and public interaction with the drainage network.
Birmingham: From Pollution Crisis to Pioneer (1850s–1900s)
Birmingham’s sanitation story is fascinating because, unlike London’s, its major crisis led directly not to a massive discharge pipe, but to a pioneering focus on sewage treatment and land irrigation.
The Minworth; Plant represents the culmination of Birmingham’s distinctive approach.
The problem in Birmingham was not primarily the Great Stink of a tidal river like the Thames, but the devastating pollution of its non-tidal river system, especially the River Tame, which quickly became a source of major legal and health crises.
1. The Early Crisis and the Legal Battles
* Initial Practice: Like most growing cities, early Victorian Birmingham relied on a mix of privies, cesspools, and middens (dung heaps), with the waste often removed by “night soil men” to be sold as fertilizer.
* The Change: As the population exploded and the use of water closets increased, the city, under the Birmingham Improvement Act (1851), began building a unified sewer network, with its main outfall at Saltley.
* The Conflict (1850s–1870s): This simply diverted the raw sewage into the River Tame. Landowners downstream, including wealthy figures like the Earl of Bradford and C. B. Adderley (later Lord Norton), saw their land ruined and their river poisoned. They successfully obtained injunctions against the Birmingham Corporation in 1870, forcing the city to stop polluting the river. This was a critical difference from London—Birmingham was legally compelled to treat its sewage locally.
2. The Solution: Sewage Farms and Treatment
The pressure of the injunctions, coupled with the political drive of figures like Joseph Chamberlain (Mayor of Birmingham), led to a radical, multi-stage solution:
A. Land Treatment (The Sewage Farm)
* In 1877, the Birmingham Tame and Rea District Drainage Board (BTRDDB) was established to manage sewage for Birmingham and the rapidly industrialising Black Country districts.
* The Board acquired a vast area of low-lying land, including at Tyburn and extending to Minworth, to create enormous sewage farms.
* The Method: The sewage was first treated with lime (chemical precipitation) to settle out the heaviest solids. The resulting liquid effluent was then spread over the land for natural irrigation and purification before being allowed to drain into the Tame.
B. The Minworth Breakthrough (c. 1900)
* While effective, the sewage farm method required huge amounts of land (over 2,000 acres eventually) and was still a nuisance. As the 19th century ended, the BTRDDB pioneered new methods at their sites, including the Minworth Greaves Sewage Farm.
* The Innovation: The BTRDDB transitioned from massive land irrigation to biological treatment using bacteria beds (or trickling filters) in the early 1900s. This process allowed the city to treat vastly more sewage in a much smaller area by using biological processes to purify the water.
* The Result: Minworth became the central hub and, eventually, one of the largest municipal sewage works in Europe, gravity-feeding the sewage from Birmingham and the Black Country for treatment, demonstrating a national leadership in the then-new science of sewage purification.
Today, Minworth Sewage Treatment Works remains the central hub of the area, a testament to Birmingham’s early municipal enterprise in public health engineering.
The Paris System: A Dual-Network & Open Sewers
Paris’s system, championed by engineer Eugène Belgrand during the urban redesign by Baron Haussmann in the 1850s, adopted a fundamentally different approach, particularly regarding street cleansing and water supply.
1. The Flushing Gutters (Bouches de Lavage)
The most visible difference is exactly what you mentioned: the routine flushing of street gutters, which still happens today.
* The Technique: Paris maintains a dual water network. It uses highly treated, potable (drinking) water for domestic use, and a separate, cheaper, non-potable water supply for municipal purposes like watering parks and, crucially, street washing.
* The Purpose: City workers periodically open kerbside valves (called bouches de lavage) to release a strong flow of non-potable water down the gutters. Workers then sweep the day’s debris—leaves, dust, and litter—into the moving current, which carries the waste into the main sewer grates. This is a deliberate, daily use of water to keep the streets physically clean and prevent surface debris from fouling the air (addressing the old Miasma concerns).
2. Sewer Design and Access
Unlike London’s egg-shaped, purely utilitarian tunnels, Paris’s main sewers were designed as underground boulevards., where access was not a problem, and sewers could easliy be cleaned.
Manholes
With perhaps the exception of the Paris sewer design of large open space, Sewers, no matter how well they are designed, block, often because they are seen as the easiest removal system for many household goods, the pipes were never designed to remove. so a method was devised to access the pipes at regulat intervals, by means of manholes In order to obtain access to sewers.
Manholes come on all shapes and sizes, circular square and rectagular, and depending on the depth of the pipe, come with a ladder built into the structure.
A Single pipe system becomes a twin pipe system
Over loading of the system by rainwater created a problem for many sewage plants, By the early 1900 it was clear, a single pipe system was now overloaded, and surface water needed to be separated into a storm stystem away from the Foul pipe,
The bylaws at the time were specific to each city, or county
Ventilation and the ‘Trap’ System
The U-Bend (or S-Trap): Sealing the Foul Air
It is here I want to return to the work Thomas Crapper did in refining the wc, by the incorporation of a U bend or water seal.
* The Problem: When WCs began flushing waste into the local drains, the highly noxious, disease-carrying gases (miasma) generated in the drains and cesspits traveled backward up the pipe and into the house.
The Solution: The U-bend (or the S-trap in earlier designs, patented by Alexander Cumming in 1775) was a genius application of simple physics. It is a curved section of pipe immediately below the WC unit designed to always retain a small amount of water . This plug of water created a physical, airtight barrier, or seal, preventing the foul air and sewer gas from entering the home, thereby making the indoor WC safe and desirable.
The Cesspit
This method started as a simple hole in the ground to hold the outflow of so many pipes, fortunately this method has evolved into the use of specalised containers that treat the outflow, storing the solid and treating the liquid so that it can be distributed onto the land by underground pipes. The tank being emptied at regular intervals by specialist contractors. Used mainly in rural areas.
The Septic Tank
The evolution of the Cesspit, we now have a mini treatment plant capable of taking not one house but many Peter Burberry’s book “Environment & Services” has a classic technical drawing of a small unit.
SUDS
It would be wrong not to include the SUD’s or sustainable Urban Drainage into the mix, where water is taken from the roof, treated and used to flush wc’s instead of using pure drinking water. Land drainage is also collected for use as garden watering,
Ventilation: Preventing Pressure and Siphonage
While the U-bend solved the local problem, it created a new one: isolating the gas meant the entire pipe system, now full of air and gas, needed ventilation.
* Siphonage: When water rapidly rushes down a pipe (as from a flushing WC), it creates a vacuum behind it. This vacuum can literally “siphon” the protective water seal right out of the neighboring U-bends in the system (e.g., in a sink or another nearby toilet), thus breaking the barrier and allowing sewer gas to enter the building.
* The Solution: The Soil Stack and Vent Pipe: To prevent siphonage and pressure build-up, engineers began installing vertical pipes, known as the soil stack or vent pipe, which run straight up through the house and terminate above the roofline .
* This pipe draws in fresh air when a WC is flushed, preventing the siphon action from pulling the trap dry.
* It also allows sewer gases, which are lighter than air, to escape safely high above the building, where they dissipate harmlessly into the atmosphere.
The requirement for proper ventilation and trapping quickly became mandatory in local bylaws, recognizing that a safe sanitary system depended not just on where the sewage went, but on how effectively the foul air was sealed off and vented away from human habitation.
Current Building Regulations
Part H of the English Building Regulations,
Connecting new pipes and networks to older system
You may be wondering why we have included this rather large introduction to the development of sewage system, and the answer is simple, they may well be still in existence, and the only solution to your new building is to connect to these older and often delicate pipes, that may well be now running at capacity, and adding your load to these older pipes, will need careful planning and possibly replacement of pipes well away from your building site.
In the advanced chapters on drainage together with Mitchells Environment and Services by Peter Burberry, we take a long look at the internal pipework, the need for venting, seals and water traps, and how we deal with toilets on a building like the Burj Khalifa in Dubia f 829.8 m (2,722 ft) almost ½ a mile high. Flushing is important, but do we need to use palatable water, here we introduce the SUDS (SuDS) or sustainable Urban drainage methods and in particular the use of none palatable water to flush toilets, and discuss the inevitable impact of Climate change, and the rise in the volume of rain water and its impact on even new systems yet alone older often delicate pipe networks.
Bibliography
* Google (2025) Gemini (2.5 Flash) [Large language model, personal communication]. Available at: gemini.google.com (Accessed: 29 October 2025).
* Burberry, P., 1997. Environment and services, 8. ed. ed, Mitchell’s building series. Longman, Harlow. (Accessed: 29 October 2025).
* Whyatt, H.G., 1941. Sewers and Sewage, 1941st ed. Sir Isac Pitman & Sons Ltd, London.(Accessed: 29 October 2025).
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