How does the sewer system work?

Our sewer system is an essential part of modern life, keeping our homes and streets clean and hygienic.

But how does the vast infrastructure that exists beneath our feet actually work? In this article, we will take a closer look at the importance of our sewer system, how it was created and how the system deals with the foul water and surface water that enter our drains.

Why does the sewer system matter?

Most of us don’t think too much about what happens to the water that collects in storm drains, gets flushed down the toilet or washes down the plughole after our morning shower. This is because most of us don’t have to think about it – as our modern sewer system takes care of all the hard work for us.

The only time we really think about our sewers and drains is when the system is less robust, or isn’t functioning correctly. In the UK, we’re fortunate to have one of the best sanitation systems in the world; in developing countries, where facilities are not as sophisticated, open trench drainage channels transport waste from the home to treatment facilities, if available – and often, these trenches can get very smelly. Some countries don’t even have the luxury of functioning sewer systems where the waste is actually treated.

As such, the modern British sewer system is essential in providing us with the quality of life we’ve come to expect: it provides us with a safe and hygienic way to dispose of waste, which in turn protects us from the risk of infection and disease, and also means we are rarely burdened with the smell or sight of wastewater. In addition, the treatment of these waters means we have reliable access to clean water for drinking and irrigation, among other applications.

When were the UK sewers built?

Sewer systems have existed in Britain in some form or another since 3,200 BC. The Orkney Islands in Scotland show signs of early drainage systems, with lavatory-like plumbing fitted within wall recesses. However, most of these primitive systems had numerous flaws, causing cholera epidemics and foul odours.

When the Romans occupied Britain from 43 to 410 AD, they brought with them their advances in cleanliness, including public bathhouses, complex drainage systems, latrines and aqueducts; however, the fall of the Roman Empire coincided with a drop in standards. A basic sewer system existed in London in the 1550s in the form of open ditches running to the River Thames, but little else was done to transform the sewerage system until the outbreak of several cholera epidemics in the 1800s.

In 1854, the contamination of a well in the Broad Street neighbourhood of London was identified as the source of a cholera epidemic in Soho. Four years later came the “Great Stink”, a period of high temperatures that created an intolerable stench from the open cesspool that was the River Thames, and which resulted in Parliament having to be closed several times.

With the need for a revamped approach to sewerage having become evidently urgent, the Metropolitan Board of Works’ celebrated chief engineer Joseph Bazalgette was given the go-ahead to create a brand new and much more effective system, which revolutionised the way we disposed of waste in the UK. It was quickly adopted throughout the country, and remains in use in London even to this day.

How does the sewer system work?

The modern sewer system owes much to Bazalgette’s pioneering work, and uses sophisticated methods to ensure that wastewater is transported and treated correctly.

Here’s how it works:

  • Wastewater disposed of via toilets, sinks, showers or baths are channelled into underground foul water drains and sewers. Separate drains and sewers are used for collecting surface water – including rainwater and melted ice – and transporting it back into the rivers and seas

  • The foul water is taken to water treatment stations, where it goes through a screening process. Debris, such as rubbish and grit, is removed from the water, which is held until the solids have separated from the liquids. These solids are then collected and often used as fertiliser

  • Waste-eating bacteria is used to break down any remaining waste into harmless matter. To do this, the water is either held in large tanks, or passed over stones like granite that are inhabited by these types of bacteria

  • The water is passed through a special tank to get rid of any remaining waste particles. Depending on its composition, the water may instead be treated with chlorine to kill off any remaining bacteria

  • After the water has been treated, it is usually returned to rivers and streams, or discharged into the sea. The thoroughness of the purification process helps to keep these bodies of water as healthy as possible

How are sewers cleaned and maintained?

The importance of the sewers makes it vital that they are regularly cleaned, maintained and kept free of blockages and defects wherever possible.

Companies like Lanes play a vital role in this. With our advanced CCTV drain survey technology, we’re able to take high-resolution images of sewer interiors to detect any signs of a blockage or a structural weakness, and determine the best ways of repairing them. If cracks are present, cured-in-place piping (CIPP) or UV lining technology can be used to resurface the pipes without the need for excavation, although full replacement of certain sewer sections may also be required on occasion.

However, matters become a lot more complicated when the drains become blocked by fatbergs, a term that refers to a giant mass of fat, grease, wipes and plastic products that are flushed down the drains and solidify into immovable objects. Fatbergs can result in foul waste flooding and pollution of the local environment, and can only be removed by manually digging them out – a difficult and time-consuming process.

How can I help to look after the sewers?

We can all make a difference in keeping the UK’s sewer system clear of these stubborn blockages by making simple adjustments to the way we dispose of common waste items. Most importantly, households and businesses alike should be conscious of the so-called ‘Big Offenders’ – the items and substances that contribute most to fatberg formation, and should therefore never be washed down plugholes or toilets under any circumstances:

  • Fats, oils and grease (FOG)

  • Wet wipes

  • Nappies and pads

  • Sanitary products

  • Tampons, applicators and wrappers

  • Condoms

  • Razor blades

  • Bandages and plasters

  • Dental floss

  • Medicines and syringes

  • Cotton buds

  • Hair

By taking the necessary steps to keep your drains clear of these obstructive items, you can do your bit to make sure the UK’s historic sewer system remains clean, hygienic and effective for many more years to come.

To find out more about the work involved in getting rid of fatbergs, visit our fatberg removal and cleaning page; alternatively, you can get in touch with us to make an enquiry about our domestic and commercial sewer services.

Call us on 0800 526 488 or use our online enquiry form, and we’ll do our best to help.

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