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Guidelines on how to reduce leaks in water networks

Onema and Irstea have published a guide containing recommendations to assist local governments in reducing leaks in their drinking-water distribution network, a necessary step to achieve compliance with the Grenelle environmental laws.

In France, a quarter of the water produced and distributed never reaches consumers. The losses are the results of leaks throughout the 850 000 kilometres of the drinking-water distribution system.

The Grenelle II environmental law has made it mandatory since July 2010 for public drinking-water services whose distribution losses are greater than the legal threshold to set up an action plan to reduce the losses. To facilitate implementation of the law and assist local governments, Onema requested that Irstea (formerly Cemagref) run a study on how to reduce leaks in drinking-water distribution systems. Investigations on actual systems were carried out with the Coulounieix-Razac intercommunal drinking-water board (Dordogne department) and its utility (SAUR), as well as with the water and sanitation board of the Bas-Rhin department.

Following the investigations, the researchers developed a model for local governments to calculate the losses in their distribution system which can range from dripping pipes and branch connections to spectacular breaks in water mains.

Division into sub-networks
The researchers recommend cutting the drinking-water distribution system into sectors, i.e. dividing it into consistent sets of sub-networks to facilitate detection of leaks, and setting priorities for the necessary work. Ranging from the design of the sub-networks and calculations on flow rates in each sector to pressure estimates and evaluation of night-time consumption, the guide proposes methods and indicators to calculate the overall losses in distribution systems.

Action plans against leaks
The four main methods to reduce water losses are discussed, namely 1) rapid intervention, 2) active detection of leaks using an array of techniques, 3) checks on pressure and 4) complete restoration or targeted renovation of the distribution system. Finally, diverse financial strategies are analysed for action plans taking into account different economic situations. Various economic-evaluation techniques are proposed to answer the most common questions of service managers, e.g. how renovation work can be funded. Other questions deal with setting up services for a group of local governments and the thresholds that determine whether a policy to detect leaks is worth the cost.

The guide is available at the water-information portal, at


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