How water companies measure leakage

Neither the UK water companies nor the industry regulators use percentage of total supply as a measure of leakage performance, as it is almost always misleading.

All companies have made efforts to reduce both leakage and customer demand in recent years. But if demand is reduced proportionately by more than leakage, then leakage in percentage terms may rise, even though both parameters have decreased.

There is no reason why leakage should relate to the total quantity of water supplied into the network. Leakage levels depend on the condition of the pipes, the pressures in the network and the efforts made by the companies to manage leakage operationally, not on the volume produced. Therefore leakage as a percentage of total production is not only misleading, it is irrelevant. The only appropriate measure of trends in leakage performance is the total volume of losses in megalitres per day (Ml/d).

Leakage is affected by the weather, especially in cold winters, and so may rise or fall from one year to the next. Nevertheless the overall trend in leakage in England and Wales over the past 10 years has been continuously downward.

The total annual leakage levels in England and Wales in the last three years were as follows:

2010-11: 3365 Ml/d 2011-12: 3108 Ml/d 2012-13: 3097 Ml/d Six of the ten water and sewerage companies achieved their lowest ever leakage levels in 2012-13. The other four all achieved their second lowest levels in that year, having achieved their lowest ever levels in the previous year. Of the nine water only companies, five achieved their lowest ever leakage levels in 2012-13. The other four all achieved their second lowest levels in that year, having achieved their lowest ever levels in the previous year.

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Notes to Editors

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