From the source to the tap

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Vannes town council water and sewage management service (DEA) runs the whole process from A to Z, from the management of resources to consumer invoicing, including the water treatment works, equipment maintenance, upkeep and development of the water supply system, metre reading etc

Tap water distributed in Vannes comes mainly (90%) from three sources:

the Meucon and Grandchamp plateaux, the river Liziec and the Noyalo reservoir.

While one of the main sources which has supplied the people of Vannes since the 17th  century is still used today, four separate resources are relied upon to satisfy the current range of water needs, of which three are run directly by Vannes town council water and sewage management service.

Photo:Le Guern Aqueduct

A water works for each resource

Rebuilt in 1997, the Lesvellec plant with a capability of 250 m3 per hour produces almost 25% of the town’s requirements.The excellent quality of sources collected from Meucon and Grandchamp requires only filter remineralisation and ultraviolet and chlorine dioxide disinfection.

2. The Liziec plant constructed in 1939 treats water from the river of the same name. As well as the traditional surface water treatments by settling and grit filtration, some additional processes were added at the end of the 80’s, in particular ozone disinfection and remineralisation before distribution.It produces 300 m3 per hour. 

3. In 1964, the Noyalo plant was built to provide water for a high-consumption industrial business and at the same time prepare for the future with a capacity of 1,000 m3 per hour. Already equipped with dynamic settling tanks, automatic grit filtration and an ozonation tower 40 years ago, additional treatments have been regularly added since then.Filtering using granular activated carbon was introduced in 1995, and offers both security and undisputable improvements in terms of quality.Today it is Vannes' main resource, capable of coping with demand in the event of failure of the other two plants but also of providing for the needs of neighbouring water supply organisations.

4. Arzal is the fourth biggest water resource, and has been in operation since 1976. This plant, which treats water from the River Vilaine, fulfils the role of backup and bulk supply, with a network extending over three départements.This extra resource constitutes an insurance in the event of potential production difficulties, in particular large-scale maintenance operations, possible pollution of water resources or a drought as in 1976. 

In 2005, by way of example, with all the resources taken into account, Vannes council produced nearly 5 million cubic metres of potable water.

From the potable water treatment plant to the consumer’s tap, the water completes a journey of several stages:

  • service water pipes ensure the transport between the plant and the main reservoirs. They generally have large diameters and are pressurised (discharge of the treated water by pumps)
  • the five reservoirs and water towers allow water storage to guarantee safe supplies to consumers, but also constitute a fire fighting reserve,
  • the distribution mains transport the water to the consumer.The network comprises primary pipes, which can allow interconnections when there are several water towers, and secondary pipes, to which the consumer networks are connected.Together they represent a vast grid system which generally functions by gravity (gravity system).

The town of Vannes has around 290 kilometres of drinking water pipes laid under the streets and roads.

The extent of the network demonstrates the amount of maintenance work (leaks, breakages, etc.) and modernisation that is continuously needed in order to guarantee an uninterrupted service to the consumer.

For this purpose, the water and sewage management service has a workforce on duty 24 hours a day, every day of the year.



Place Maurice Marchais

Tél. : 02 97 01 60 00



Monday to Friday from 8h to 12h15 and from 13h15 to 18h.Saturday morning from 9h to 12h.



7 rue Joseph Le Brix

Tél. : 02 97 01 60 00


Ouverture :


Monday to Friday from 8h15 to 12h15 and from 13h15 to 17h.


Permanence of the state civil service, Saturday 9am to 12pm.Are given priority: the declarations of birth and death as well as passport applications (by appointment).


Saturday morning, home phone from 9h to 12h.