Mains water and sewerage services are provided by Yorkshire Water. Drinking water is supplied from Bullamore Reservoir (a system of four covered concrete cisterns on the hillside east of the town) which are fed with water from the River Ure via Thornton Steward Reservoir. Until around 2006, Northallerton received its water from Cod Beck Reservoir near Osmotherley. The storage at Bullamore was doubled in 2006 in anticipation of the closure of Cod Beck Water Treatment Works; Bullamore Reservoir is also the primary source of water for Thirsk. Sewerage is processed at Northallerton and Romanby Sewage Treatment Works, both in Romanby, which discharge into Willow Beck, a tributary of the River Wiske.