Incorporated under the Sibu Water Board Order, 1959 made under Section 19 of the Water Supply Ordinance 1959 (Cap. 141) and re-incorporated under the Sibu Water Board Order, 1995 made under Section 19 of the Water Ordinance 1994 when the Water Supply Ordinance 1959 was repealed. The constitution of the Board was further amended vide Sibu Water Board Order 2002 and Sibu Water Board Order 2005.

A body corporate established by the Yang diPertua Negeri as the water authority to administer, manage and supervise all water works situated within the area specified below: Commencing from a Trig point numbered TT352 at the Sibu/Kanowit District Boundary on the true left bank of Batang Rajang about 1300 metres from East of Sungai Pak; thence on a South/ Westerly direction following the Sibu/Kanowit District Boundary until it reaches Trig marked N134 on the common Divisional Boundary of Sibu/Sarikei; thence following the Sibu/Sarikei Divisional Boundary on a West/Northerly direction until it reaches the confluence of Loba Singat at Batang Lassa; thence on bearing 90 degree for a distance of 46 Km to reach a point at ‘A’ on the common District Boundary of Sibu/Dalat; thence following the existing Sibu/Dalat District Boundary on a Southerly direction for a distance of approximately 45 Km; thence following the existing Sibu/Kanowit District Boundary on a Southerly direction for a distance of approximately 10 Km to reach the Trig marked TT352, being the point of commencement.