The water cycle

On average we supply more than one thousand litres of water a week to each of our 8.8m drinking water customers. We get this water from rivers and underground stores and turn it into high-quality drinking water that we send to your home, work and school for you to use.

Once you have used the water, we recycle it safely back to the environment.

Providing you with water and taking it away again once you have used it, forms part of a larger process called the water cycle.

The water cycle 

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1. Evaporation

Water is heated by the sun and evaporates to become water vapour. As it’s light, it floats into the air – just like steam rising from a kettle.

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2. Condensation

As the water vapour rises into the air, it gradually cools and collects together to form tiny droplets of water through a process called condensation. It is this process that causes your bathroom mirror to steam up when you have a bath or shower.

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3. Clouds

Billions of these tiny water droplets crowd together, which creates clouds.

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4. Rain

When the billions of tiny droplets become too heavy, they fall onto the ground as rain.

Did you know?

London actually receives less rainfall than Rome, Istanbul and Dallas and half as much as Sydney.

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5. Rivers

When rain hits the ground, it flows into rivers, streams and underground stores, also known as ‘aquifers’. River water is clean enough to support a variety of wildlife, but isn’t safe to drink.

Did you know?

80% of the water we supply to London and the Thames Valley comes from rivers and 20% comes from underground sources called ‘aquifers’.

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6. Water treatment works

The water we treat and send to your home, school or office for you to use, is taken from rivers and underground stores. It is then put through a treatment process to turn it into top quality drinking water.

Did you know?

We have a team of water samplers and scientists who carry out more than half a million tests on our water every year.

View the water treatment cycle
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7. Water distribution

We then pump the clean water into our network of pipes and storage reservoirs. The water is not seen again until it reaches your tap – this guarantees that the water you drink remains clean and fresh.

Did you know?

We have 20,000 miles of water pipes, some of which are over 150 years old. We have already replaced over 1,300 miles with new plastic pipes since 2006. This has helped reduce the amount of water leaked by 27%.

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8. Water use

Baths, showers, washing up, cleaning clothes and flushing the toilet all use large amounts of water. Once you have used the water, it turns into ‘wastewater’, which we then collect, transport, treat and return safely back to the environment.

Did you know?

On average, each of our 8.8 million customers uses 157 litres of water a day. This is well above the national average and the Government’s aim of 130 litres.

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9. Treating sewage

The sewage goes into our network of sewer pipes, which take it to a sewage treatment works where it is treated so that it can be put safely back into rivers.

Did you know?

We have over 43,500 miles of sewers, 2,530 pumping stations and 1.2 million manholes that help take the wastewater to our sewage treatment works.

View the sewage treatment cycle
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10. Completing the cycle

The river continues its journey back to the sea where the cycle starts again; where water evaporates to form clouds, condenses to droplets and eventually falls as rain on to the ground.

Did you know?

Many parts of the country, including our region, are classed as ‘water stressed’. This means that if we all carry on using the same amount of water, or more, there is a risk that in the future there may not be enough to go around.

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