Frequently asked questions

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On this page you can read answers to the most frequently asked questions about the Thames Gateway Water Treatment Works.

Our Thames Gateway Water Treatment Works opened in June 2010.

We begin by taking a mixture of salty and fresh water from the tidal River Thames, then treat it using various cleaning and filtering processes, as used in all our treatment works.

We remove the salt using a process called reverse osmosis. This involves forcing the water at high pressure through very fine membranes, which hold back the salt and other molecules. The treated water is then re-mineralised so that it has similar properties to other local supplies. Following this, we purify the water to ensure it is safe to drink, before putting it into our supply network.

The technology we are using to remove the salt includes a four-stage filtration process, as opposed to the two or three stages used in most similar works. This is more efficient, meaning that we can turn 85 per cent of the water we take from the River Thames into drinking water, rather than the 50 per cent typical of other similar treatment works around the world.

Our desalination plant in east London turns a mix of salt and fresh water from the tidal River Thames into high-quality drinking water.

The facility is capable of putting an additional 150 million litres of water into supply - enough water for one million people’s daily needs.

This plant is one of several long-term measures to conserve and manage water supplies for London and the Thames Valley.

We have beaten our leakage target for six years running, reducing leakage by more than a third since its peak in 2004, and helped promote water efficiency across our region - two areas on which we continue to make progress.

However, the benefits still do not match the potential shortfall in a drought between the amount of water our customers need and what we can supply to them.

All of London's available fresh water supplies are already in use. When needed, our new treatment works takes water from the tidal part of the River Thames, which is a mixture of salty and fresh water.

We then remove the low level of salt to produce drinking water - a process called desalination. This stretch of the river provides a potentially limitless source of water.

The water is slightly softer. This means that, depending on the proportion being mixed with our other supplies, you might need to use less soap and detergent to generate a lather.

When working at full capacity, the works will be capable of supplying 150 million litres of water per day - enough to supply about one million people or 400,000 households.

When used at full capacity, the works will supply people in parts of the following London boroughs and district councils in and around north-east London: Broxbourne, East Hertfordshire, Epping Forest, Enfield, Hackney, Haringey, Havering, Newham, Redbridge, Tower Hamlets and Waltham Forest.

Also in this section

Why does London need more water? How the treatment works operates