Water leaks, broken pipes, a scourge in Biterrois

Le président du Sivom Christian Séguy (à G) et Sébastien Chazalon (à D) de Suez dans la station de pompage. – F.Faux

Cessenon-sur-Orb perdait la moitié de son eau dans les canalisations alors que le Sivom d’Ensérune, lui, est complètement "étanche"… Tout est une question de travaux.

Water is a bit like a household budget. To avoid being in deficit, we must watch over revenues – groundwater pumping – while controlling expenses: consumption, and leaks on the network. At Sivom (intercommunal union)  d’Ensérune, which supplies the taps of 11 municipalities stretching from Quarante to Vendres, west of Béziers, the latter point’ nbsp;has become an obsession.

"What is important is to be informed, instantly, about changes in throughput in our network distribution, warns Sébastien Chalazon, employee of Suez, who manages this delegation for Sivom. As soon as cubic meters are lost, we must intervene."

He opens the doors to a small premises located near the Tabarka bridge, in the town of Maraussan. Next to it, a small hill hides a 1,000 m3 reservoir, connected to the two boreholes which draw water about fifteen meters below the alluvium of the Orb. In the basement, five pumps each pump out 250 m3 every hour, with deafening noise, adapting to the pressure of the network. Management is automatic, interventions are done remotely.

"There are two main causes of leaks, continues Sébastien Chalazon. Defective seals that need to be changed, but also pipes that simply break. When it is very dry, in summer, or very humid, in winter, the clay soils here move a lot. On this 72 kilometer network, this represents between 15 and 30 interventions per year". And to ensure that this number does not increase in the future, we also need to invest. Sivom has therefore chosen to use cast iron pipes and not PVC: "It’is more expensive, but also more solid. Cast iron can last a century, while with PVC, depending on how it is installed, you can divide that& ;nbsp;lifespan by three".

Concretely, this means streets gutted three times more often to repair leaks. But you still need to know where to intervene. Traditionally, networks are equipped with an acoustic system placed on the valves – "ears" – which allow you to listen to leaks. Today, smart meters installed at regular intervals make it possible to identify flow variations in real time, much more precisely. There are around a hundred on this network.

The result of all these actions is visible today. In a study of intercommunalities in France, published in March 2024, the Sivom of Ensérune achieved a rate of return (ratio between the water which is injected into the network and that which finally reaches users) of 96.7%. One of the best in the department. If we look closely at the municipalities of western Hérault, we can spot significant differences. Among the best ranked, we find Vailhan (97.8%), Vendres (93.2%) or St-Pons de Mauchiens (92.5%). At the other opposite are Berlou (50.4%), Hérépian (54.8%) and with only 47%, or more than half of the water that vanished into the wild, Cessenon-sur-Orb. This town, last summer, made headlines by chartering trucks to supply itself with drinking water.

The mayor, Marie-Pierre Pons, is hardly surprised, but wishes to correct: "We had done work from 2021, for 800,000, and we only went from 46% to 47%! It’was really upsetting." Because the problem, in fact, was elsewhere, and it has just been discovered: "There is a month, a citizen called us because there was water – a real stream – which flowed in the street in front of his house. We brought in a company, found the pipe, and the leak… Since then our consumption has gone from 600-650 m3 per day to only 480 !" Which underground sinkhole was filled with this water before it reappeared on the surface? How long was this mega-leak present? ;nbsp;? The mystery remains. "But with smart meters, admits Marie-Pierre Pons, on would have seen her more quickly.