Amersham Water Hardness & Quality Report (2026)

Amersham, the Chiltern Hills town in the Misbourne valley in south Buckinghamshire — renowned for its historic old town, its Metropolitan line station and its Arts and Crafts character — is supplied by Affinity Water from the Chilterns Chalk Aquifer. The River Misbourne is a classic chalk stream — one of the UK's rarer intermittent chalk stream systems — draining the Chiltern chalk dip slope from Great Missenden south-east to Amersham and Chalfont St Giles. Affinity Water abstracts from chalk boreholes in the Misbourne valley and on the Chiltern chalk plateau above Amersham, distributing treated supply through the south Buckinghamshire network. At 182.5 mg/L with TDS 416.4 mg/L (ratio 2.28), Amersham's supply is moderately hard chalk water — notably softer than Berkhamsted (241 mg/L) in the Gade valley, reflecting the different position of the Misbourne catchment on the Chiltern dip slope, which produces less confined and somewhat softer chalk groundwater than the upper Gade or Bulbourne valleys to the north-east. The lower TDS-to-hardness ratio (2.28) also suggests limited sulphate contribution — a characteristic of the cleaner dip-slope chalk in the south Chilterns.

The Cretaceous Upper Chalk of the Chiltern dip slope in the Amersham area is an unconfined aquifer at 20–50 m depth, recharging directly from the chalk plateau above the town. Chalk groundwater here achieves calcium bicarbonate concentrations of 175–190 mg/L — less concentrated than the deeper confined or more mineralised chalk zones of east Hertfordshire or the London Basin rim, because the Chiltern dip-slope chalk in south Buckinghamshire has a shorter groundwater path before abstraction and less mineral enrichment from overlying Tertiary formations.

At 182.5 mg/L Amersham's water is moderately hard and limescale management is a steady routine. Kettles benefit from descaling every four to six weeks with a citric acid tablet. Shower screens develop moderate calcium spotting that responds to regular white vinegar treatment. Washing-up liquid lathers adequately. Combi-boilers benefit from scale inhibitor protection. Amersham's Chiltern village and commuter town character — the beamed inns of the old town, the Metropolitan line that has shaped its character since the 1890s, the Misbourne water meadows — is supplied by the chalk stream's moderately hard water, a defining feature of the Chilterns chalk landscape.