water main
From Longman Dictionary of Contemporary EnglishRelated topics: Civilwater mainˈwater main noun [countable] TECa large underground pipe that carries the public supply of water to buildings a burst water mainExamples from the Corpuswater main• A water main froze and broke in the neighborhood, and the streets have been flooded for two days.• Building London's ring water main is not a job for the fainthearted.