Preston Water Hardness & Quality Report (2026)

Preston's water supply is managed by United Utilities, the water and wastewater utility serving the whole of North West England. Supply is drawn primarily from the Rivington Reservoir group near Chorley — a system of six reservoirs originally built by Liverpool Corporation from the 1850s and subsequently incorporated into the United Utilities network — supplemented by Pennine upland catchments and the wider North West aqueduct grid, including contributions from Lake District sources. Water is treated at Rivington Water Treatment Works before distribution through Lancashire's network to Preston and the surrounding areas of Central Lancashire.

Preston's water hardness of 35 mg/L (2.5°Clark) reflects the geology of the western Pennine catchments. The Rivington and surrounding Lancashire moorlands are underlain by Carboniferous Millstone Grit — a coarse-grained, calcium-poor sandstone highly resistant to chemical dissolution. Rainfall runs off these impermeable moorland surfaces quickly, carrying minimal dissolved minerals. There is no chalk or limestone in these catchment areas, and the result is a supply classified as very soft by the Drinking Water Inspectorate (DWI).

Limescale is not a meaningful concern for Preston households. At 35 mg/L, limescale accumulates very slowly — kettles may need descaling only once or twice per year, and limescale deposits on taps and showerheads remain negligible with normal cleaning. Combi-boiler heat exchangers in Preston properties are under very little stress from limescale, helping maintain boiler efficiency throughout the appliance's working life. Washing-up liquid lathers freely with minimal product. The main practical consideration for Preston residents is that soft water can be slightly corrosive to copper and lead service pipes in older housing stock — running the kitchen tap briefly before drinking is sensible in any pre-1970 property that has not had its pipework updated.