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Our leakage performance

How we're tackling leakage

Every day we supply 2.6 billion litres of water, but not all of that gets to our customers. At the moment, we leak almost 24% of the water we supply. We know it’s not acceptable to be losing so much precious water and we’ve got a plan to fix it. It’s not going to be quick, but we’re making progress.

We work with Ofwat, our regulator, to agree stretching targets for reducing our leakage. Through careful planning, better use of data and new ways of working, we met our target in 2020 and 2021. In 2020/21, we reduced the amount of water leaked by almost 6%, or 37 Ml/d.

Going forward, our aim is to reduce our leakage by more than 20% between 2020 and 2025, and by 50% in the longer term.

Our final leakage position for 2021/22 will be available after we’ve completed our year-end assurance and audit process. Following our audit, we’ll publish our final leakage performance for the year in our Annual Report in July 2022 and will also update this report.

How can you help?

You can help us find leaks and save water. If you spot a leak, please let us know.

Report a leak online

You can also prevent leaks in your home by being ‘water smart’ and protecting your pipes in winter to stop them bursting.

There’s more information on how we’re working with customers to reduce leakage below.

What is leakage?

Leakage is lost water – that’s all the water not making its way to customers. Most of this water leaks from our ageing pipes, but sometimes it’s stolen or we’re just not as good as we should be in understanding how much water customers are using.

Leaks are caused by various things, including:

  • Old or weak pipes
  • Natural wear and tear on pipes
  • Sudden heavy traffic causing movement in the ground
  • Temperature changes, which cause pipes to swell and shrink
  • High pressure or sudden changes in pressure
  • Extreme weather events, like freeze-thaws.

Types of leaks

A diagram showing different types of leak.

Over 95% of leaks are never seen by customers. They’re often smaller, underground and harder to find. Visible leaks – the ones that do reach the surface – are larger, but they don’t lose as much water. This is because they’re reported to us and we start to fix them soon after they appear.

Customer leaks are not on our network, but we work with our customers to repair them where we can. In some cases, we’ll do this free of charge. You can also read our guide on fixing a leak at your property.

Illustration of a Thames Water engineer

What are we doing to reduce leaks?

New leaks can appear at any time. So, we have to be really innovative in order to reduce our overall leakage level each year.

We’re also working with customers to help them save water and use it more efficiently. This helps to reduce water and energy bills too. For example:

  • Our smarter home and smarter business visits help our customers understand how much water they use. Our water efficiency teams fit water saving devices and give personalised advice on how to save water
  • We’ve installed over 500,000 smart water meters to help customers track their water use
  • We offer guidance on how to save water by being ‘water smart’ and on protecting your pipes in winter to stop them bursting 

Why reducing leakage matters

Not only can water leaks can cause serious damage to homes and properties, water is an extremely precious resource. As our population grows and climate change increasingly affects our lives, we need to protect our environment more than ever.

Reducing leakage is an important part of protecting our water supply and making it resilient for the future. Read more about our wider plans to look after water.

How do we measure leakage?

We measure leakage in megalitres, or millions of litres, per day (Ml/d). One megalitre is equal to around 12,500 baths, or 40% of an Olympic size swimming pool.

We estimate leakage by comparing the volume of water we put into supply against the amount we estimate is being used. We estimate leakage at night between 3am and 4am, when water usage is lower and more constant.

Leakage levels change throughout the year, so to measure and report our performance we take our daily leakage figures and average them for each month and in turn across the year.

How do we fix leaks?

Here’s our process:

  1. Locate: We’ll find a leak, or it’ll be reported to us - you can report a leak online.

  2. Assess: One of our leakage teams will check what needs to be done to fix the leak and how urgent it is. We prioritise repairs based on things like the amount of water being lost, the effect on customers’ water supply, the complexity and the location.

  3. Plan: We’ll always plan the repair as quickly as possible, and in a way that’s least disruptive to our customers. We’ll also send letters to customers near the site, so they know what’s going on. However, it’s not just us who are involved in the process and it can take time to plan the logistics.

    We may need to work with the council and highways authorities if we need to close a road, for example. Or we may need to coordinate with other utilities, if we’re working near one of their pipes, so they can take the right safety precautions. Sometimes we have to balance whether it’s better to do the repair during the day or at night. Closing roads at night helps us to avoid disrupting traffic and water supplies during the day, but repairing pipes at night may create noise when customers are sleeping.

  4. Repair: Once the plan is in place, we’ll send a repair team to fix the leak. This might involve turning off the water or redirecting water around other pipes. Sometimes the repair teams need to dig down to the pipe by hand to be safe, particularly if it’s in a tricky position and surrounded by other utility pipes like gas mains. When the pipe has been fixed, we resurface the road which can take time to set safely.
Did you know that some of our pipes are up to 3 metres underground?

The information provided is, to the best of our knowledge, accurate, but may be subject to change from time to time. The information does not represent formal annual regulatory reporting.