Reducing leakage

We reduced leakage further in 2009/10, beating our leakage target for a fourth successive year, despite one of the coldest winters in recent years.

Annual average leakage for the year was 670m litres per day (Ml/d), against the target of 685 Ml/d. This represents a reduction of 29 Ml/d below the level reported for the previous 12 months, and brings our total leakage reduction over the last five years to 245 Ml/d – a fall of 27 per cent.

We made good progress on tackling leakage for the first eight months of the year, but in December temperatures plummeted, and from then we experienced a sustained period of particularly cold weather. This was sometimes accompanied by heavy snow, which made it particularly difficult to detect and repair leaks.

Average winter temperatures were the coldest since we first began analysing leakage data 25 years ago.

We managed our response by following our winter contingency plan, which involved using weather forecast data to predict the number of burst mains and deploying staff from other parts of the company. This enabled us to reduce leakage by nearly 300m litres per day between January and the end of March.

In addition to general leakage repairs, we continued our high-profile work to replace many of London's oldest water mains. We believe this is the only way to make long-term, sustainable leakage reductions.

Our Victorian Mains Replacement work has played a major part in reducing leakage.

During the year, we have:

• Continued our work to replace Victorian mains, renewing more than 375km of London's oldest pipes and bringing the total to more than 1,865km over the last five years.

• Detected and repaired almost 26,600 leaks, fixed a further 19,000 reported to us by customers and helped identify or repair 8,000 leaks on customers' pipework. On average, we fixed a leak every ten minutes.

• Carried out a further 127 repairs on our largest 'trunk' mains.

• Made further leakage savings by better regulating pumping pressures in London.

• Improved the accuracy of metering in our pipe network to ensure we can better target leakage repairs.