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8. Water pollution from drains

All the drains we see on roads eventually empty into the Thames or its tributaries. Lots of pollutants, like oil and chemicals, can get washed down those drains when it rains. Sometimes, waste from people’s homes can go down the drain if the toilets are not connected up properly. Any waste that gets into rivers may harm the wildlife that lives there.

In Victorian times, the Thames became very polluted. Filthy water from factories and the newly invented water closets (toilets) poured straight down drains into the river, killing all the wildlife. Londoners still drank river water and thousands died of cholera. In the 1960’s, a big clean up began: sewage treatment was improved and factories had to reduce their polluting discharges. The Thames is now one of the cleanest city rivers in Europe. However, pollution does still enter the Thames in London through the drainage system.

There are several ways in which drains emptying into the river can cause pollution.

Surface water from roads and roofs
The rain that falls in a town normally gets channelled down gutters into the drainage system and is put straight into to the river. It does not get cleaned first. This means that any dirt or oil on the roads gets washed straight into the river system.

Pollutants poured down drains
Some people use a drain in the road outside or in their garden to dispose of oil or dirty water. This generally goes straight into the river.

Bad plumbing
Badly connected toilets can also cause pollution. Sometimes bad plumbers or people doing DIY connect their toilet systems to the drainage system instead of the sewerage system. This means that sewage goes directly into the nearest river. This problem occurs mainly on the tributaries of the Thames.

Sewage pollution
In much of London, the drainage and sewerage systems are combined. This is good news in some ways, as it means that a lot of the dirty water that goes down drains is taken to the sewage works where it is cleaned before being returned to the river. But when rain is heavy, the system gets too full and raw sewage overflows through storm drains into the river. This sewage is mixed with other pollutants such as oil from the roads and can be a deadly mixture.

The reason that London’s sewerage and drainage system cannot cope any more is because it was built in Victorian times to serve a much smaller population. More people means more sewage and because more of the land is covered in concrete, more rain water gets channelled down the drains.

The Environment Agency keeps an eye on levels of pollution – it has eight monitoring stations in the London area which monitor how much oxygen there is in the water. The information is fed to a computer. If levels drop, they send in two boats, Thames Bubbler and Thames Vitality, which pump oxygen into the river where it is needed. This system is world famous and has prevented many fish deaths. However the long term solution is to replace the old Victorian sewerage/drainage system with a modern system that does not allow sewage into the river.


* raw sewage reduces oxygen levels, suffocating river wildlife. This is because sewage contains lots of bacteria who gobble up all the oxygen * oil can coat the feathers of river birds, causing them to drown or die of hypothermia * river pollution makes the river look and smell bad

What we can do?

* don’t put oil or water containing dangerous chemicals down the drain – take it to a used oil bank. For information on your nearest one, call the Oil Bank Line on 0800 66 33 66 * employ a qualified plumber when installing new toilets * report any river pollution you see to the Environment Agency Hotline on 0800 80 70 60 * support improvements to the sewage system, which improves water quality in rivers. This might mean your family has to pay higher water bills!