Farnham Water Hardness & Quality Report (2026)

Farnham, in the Waverley district of west Surrey near the Hampshire border on the River Wey, is supplied by South East Water from the North Downs Chalk Aquifer and Lower Greensand formation of west Surrey. South East Water draws from chalk boreholes in the Cretaceous Chalk of the west Surrey Hills — the chalk escarpment and dipslope of the Surrey North Downs at Runfold and the Hog's Back — and from the Lower Greensand aquifer of the Blackwater valley and Farnham Terrace area. The chalk of the west Surrey hills produces moderately hard groundwater from chalk dissolution, and the Lower Greensand adds a slightly softer contribution. South East Water distributes through the west Surrey supply network to Farnham and the south-west Surrey towns.

Farnham's hardness of 192.5 mg/L (13.5°Clark) reflects the North Downs Chalk Aquifer and Lower Greensand of west Surrey in South East Water's Farnham supply zone. The Drinking Water Inspectorate (DWI) classifies this supply as moderately hard.

Limescale is a regular household concern in Farnham. At 192.5 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 Farnham households.