Heston Water Hardness & Quality Report (2026)

Heston, in the London Borough of Hounslow in outer west London near Heathrow Airport, is supplied by Thames Water from the River Thames storage reservoirs at Hampton and Walton-on-Thames and from the North Downs Chalk Aquifer of the Surrey and Berkshire chalk. The Hampton reservoir complex is one of Thames Water's principal supply reservoirs, storing Thames water carrying chalk-stream calcium from the Wey, Mole, and chalk-stream Thames tributaries. Thames Water supplements with chalk borehole groundwater from the North Downs chalk of Surrey. Heston's outer west London Hounslow position in the Heathrow corridor is supplied from the Hampton reservoir network with moderate chalk groundwater blending, producing a moderately hard supply typical of the outer west London Thames Water zone.

Heston's hardness of 195 mg/L (13.7°Clark) reflects the River Thames storage reservoir supply and moderate North Downs Chalk groundwater blending in Thames Water's outer west London Hounslow distribution zone. The Drinking Water Inspectorate (DWI) classifies this supply as moderately hard.

Limescale is a regular household concern in Heston. At 195 mg/L, limescale forms in kettles within three to four weeks and monthly descaling is sensible. Combi-boiler heat exchangers accumulate deposits at a moderate rate; annual servicing is recommended. Showerheads and taps develop regular deposits. Washing-up liquid lathers moderately. Using Calgon monthly in the washing machine and a regular descaling routine is appropriate limescale management for Heston households near Heathrow.