The dripping tap, the leaky drain, the water damage… it’s the bane of co-ownership. At least 13 million water leaks occur each year in collective housing, according to projections by Ista, a specialist in the individualization of water and energy consumption in collective housing. Based on information provided by 1.2 million homes equipped with remote-reading water meters, the company determined that 11.9% of homes suffered at least one water leak in 2023.
What do we know about these leaks? Overall, each affected home has about 6-7 leaks, most of which are small. These insidious, low-flow leaks (faucet or drain) account for nearly 80% of detected leaks, and if left unseen, they can end up creating a large volume of lost water. Ultimately, the 10% largest leaks account for 90% of the total volume of lost water. “Our meters with their on-board intelligence accurately determine the presence of leaks by focusing on consumption differences in the middle of the night during slower periods, explains Laurent Sireix, president of Ista France. During the day it is difficult to analyse the differences in consumption”.
From single to double depending on the region
Geographically, we observe very strong regional disparities, with percentages of homes that have suffered at least one flight ranging from one to two. If Pays de la Loire (6.3%) and Brittany (7.1%) are doing well, the figures rise to 13.4% in Île-de-Frannce and 13.2% in Bourgogne-Franche-Comté. “This is the first time we have studied regional differences and therefore we do not yet have all the explanatory elements, admits Laurent Sireix. But the high presence of limescale is generally an aggravating factor, as are the average age of the homes and the level of maintenance of the taps. Finally, the occupancy rate of the home also plays a role: the more regularly we use water, the greater the risk.
One thing is certain: when a leak occurs, it represents a cost. At a rate of 20 million m3 wasted according to Ista projections, this would be equivalent to almost 95 million euros wasted. The average leak lasts 8 days and represents almost 1,500 litres of water lost. These leaks mainly concern cold water networks (based on an average price of €4.3/m²), but also hot water networks, whose consumption is measured separately and which is billed on average at €15.7/m². Because a leaky mixer also wastes hot water.
Water consumption side (see maps below)regional disparities remain significant even with Île-de-France being particularly greedy like Nouvelle-Aquitaine, Bourgogne-Franche-Comté or even PACA. On the contrary, Pays de la Loire is the cheapest region. “In 2023, a year of water restrictions, we observed a very sharp drop of 30% in water consumption in Occitania and a more moderate drop of 9% in the Pays de la Loire, underlines Laurent Sireix. Surprisingly, this consumption increased by 7% in Normandy and New Aquitaine.”