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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, almost 24% of the water we supply is lost through leakage – which is a combination of water lost on our pipes, water lost on customers’ pipes and an element of unmeasured consumption (46% of billed customers are unmeasured with 17% of individual customers having smart meters).

In 2022/23 we’ve reduced leakage by 10.7%, calculated using a three-year average from the 2019/20 baseline, which was below our target reduction of 14.1%. Unfortunately, like many other water companies 2022/23 was an exceptional year for severe and unprecedented weather conditions. Firstly, in July 2022 we experienced a national drought which lasted through to October. During the winter we had a very cold winter event in December and a second event in January resulting in a 40% increase in leakage. Despite delivering 25% more activity in 2022/23 we fell short of our performance commitment to achieve a 14.1% reduction in leakage.

Noting the substantial risk this under-delivery places on the target for the remainder of the AMP, 2023/24 and 2024/25, (due to the three-year average calculation) critical reflections on year three have seen us evolve our leakage recovery plan to a ‘Leakage Transformation Plan’. We do remain committed to do everything that is reasonably practicable to deliver the overall leakage reduction and end the AMP in line with our original annual average target value. So far this year (2023/2024) we have reduced leakage by over 50 Ml/d from our starting point in April to end of September.

Our Leakage Transformation Programme is in full flight and focuses on building sustainable foundations and new ways of working. The first programme areas to go live are:

  • Finding and fixing the right leaks, faster – as part of this initiative we have issued a new prioritisation matrix for grading leaks. This focuses on the priority of the leak based on the volume of water lost helping us to maximise leakage reduction but also to improve the speed of response for leak repairs;
  • Understand leakage and consumption – as part of this initiative we are utilising our smart meter data to provide insight into demand and consumption;
  • Build sustainable foundations –changing our ways of working to deliver sustained leakage management and to set us up for long term success. A new leakage operating model will result in coordinated decision-making, improved awareness across our network, and will focus on delivering improvements in the most effective and efficient way possible.

How can you help?

You can help us find leaks and save water. If you spot a leak, please let us know through our view and report a problem page on our website.

Report a leak online

You can also prevent leaks in your home by being ‘water smart’.

We’ve also recently launched our ‘Toasty tips for saving water this autumn’ campaign. This campaign provides important information about the steps you can take to make a difference this autumn and save water.

What is leakage?

Leakage is lost water – that’s all the water not making its way to customers. Much of this water leaks from ageing pipes or pipes that have been damaged because of the very hot summer and/or very cold winters (such as those seen in 2022) that we have recently seen. But sometimes 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; and
  • Extreme weather events, like freeze-thaws.

Types of leaks

A diagram showing different types of leak.

Over 95% of leaks are not seen by customers. They’re often small, underground, and hard to find. Visible leaks – the ones that do reach the surface – are larger, but they don’t normally lose as much water. Our field teams work day and night to find as many leaks as possible. We also use artificial intelligence to help us find and fix large leaks faster. Our customers help too. They often report leaks to us and we start to fix them soon after they appear.

Customer leaks aren't on our network, but we work with our customers to repair them where we can. 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?

We’ll be replacing 112km of our leakiest water mains pipes across London. That will help us save 27.8 million litres of water every day, equivalent to 11 Olympic-sized swimming pools

We’ve installed over 900,000 smart meters across the Thames Water region, with 150,000 installed during 2022/23. A meter reduces average water use in the home by 13% and it’s an important tool to indicate leaks on customers’ pipes by identifying unusual water flow. The more meters we install the more leaks can be fixed.

We’ve introduced new ways of working and have insourced our repair and maintenance teams to increase control and efficiency of activity.

We’re bringing forward new innovations to reduce our overall leakage level. We’ve partnered with FiDO and Microsoft to drive down leakage. FiDO is an advanced water leak detection technology that can predict leak probability and leak size.

Why reducing leakage matters

Not only can water leaks cause serious damage to homes and properties, but water is also 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. You can 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 (Report a leak).

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 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 seeks to minimise disruption 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 London’s pipe network is made up of over 139,000km of water and waste pipes, with many dating back to the 1800s and early 1900s

The information provided in this report 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.