The Water and Sewerage Company Inc. (WASCO) was first started in 1965 as the Central Water and Authority (CWA). Under the portfolio of the Ministry of Health (MoH) with responsibility for the provision of portable water supplies and conservation, augmentation, distribution and proper use of water resources including preservation and protection of gathering grounds. The Saint Lucia Central Water Authority was constituted under the provisions of the Water Authority Act. No. 24 of 1964.

Prior to 1965, the water supply was the responsibility of the Castries City Council (CCC).  According to the Castries City Council records, pipe borne water was first brought to Castries in April 1848. The inhabitants of the island drew their water from main rivers, small streams or ponds. By 1915 the majority of the other towns and villages had some form of simple pipe borne water supply. 

In 1984 the Government of Saint Lucia (GoSL) enacted legislation to make the Central Water Authority (CWA) a statutory body responsible for the combined services of Water and Sewerage. It was renamed; the Water and Sewerage Authority (WASA), it was established as a statutory body headed by a Board of Directors reporting to the Ministry of Communications, Transport and Public Utilities.  During the existence of the Authority, several projects were undertaken including the construction of the John Compton Dam in Roseau.

The Sarot Treatment Plant was commissioned in 1972 along with a 14 inch Ductile Iron Transmission main from a one million gallon storage tank at Ciceron to Cap Estate. This new facility served residents from Castries to Cap Estate from its inception in 1992 to 1993 when the new Treatment plant at Ciceron was commissioned Thomas R Theobalds Treatment plant.

In October 1999, the Government of Saint Lucia restructured the water sector by establishing a new entity - the Water and Sewerage Company, Incorporated (WASCO).  WASCO is incorporated under the Companies Act and regulated in accordance with the provisions of the Water and Sewerage Act (2004). 

Today the Water and Sewerage Company Incorporated (WASCO) falls under the portfolio of the Ministry of Agriculture, Fisheries, Physical Planning, Natural Resources and Co-operatives.