The sewer system was installed in 1878 meanwhile, but initially limited to the area around rue d'Aumale, the Condé Hospice and the rue de Paris, now known as the avenue du Maréchal Joffre. It was extended to the entire town in 1910 through a state subsidy financed by a tax on racetrack bets. A sewage treatment plant was built in 1969 at La Canardière, then moved to Gouvieux in 2006. This 22 km network is administered by a regional agency, the syndicat intercommunal pour le traitement des eaux de la vallée de la Nonette (SICTEUV), which covers Apremont, Avilly-Saint-Léonard, Chantilly, Gouvieux et Vineuil-Saint-Firmin.