The Isle of Man Water and Sewerage Authority (Manx: Lught-reill Ushtey as Sornaigys Ellan Vannin) was the statutory board responsible for water supply and sewage disposal in the Isle of Man.

In 1985 the gas undertaking was privatised, and the authority reverted to its original title.

[5] The water supply system starts with four impounding reservoirs (operational out of seven owned by the authority) located in the uplands of the Isle of Man, the first of which was constructed in 1875, and the most recent, Sulby Reservoir, in 1982.

From the treatment centres, the water then flows to 33 underground service reservoirs.

Gravity or one of thirteen pumping stations then take the water to its end-users.