Chertsey Water Hardness & Quality Report (2026)

Thames Water supplies Chertsey, a historic market town in north Surrey on the River Thames at the head of Chertsey Meads, from the River Thames abstracted at Walton-on-Thames and treated at Walton Water Treatment Works, distributed via the Thames Water north Surrey network. At 251.5 mg/L (17.6°Clark), Chertsey's water is very hard, reflecting the chalk-dominated Thames catchment and the North Downs Chalk aquifer contributions that characterise all Thames Water supply zones in north Surrey between the river and the Downs escarpment.

The River Thames at Walton carries chalk-derived hardness accumulated from the Chiltern Chalk, North Downs, and Berkshire chalk catchments throughout the upper Thames. The North Surrey Chalk — a buried extension of the North Downs beneath the Thames terraces and alluvial plain — contributes deep groundwater with high dissolved calcium bicarbonate content to the supply blend. In Chertsey, positioned at the Thames riverside directly between the river abstraction point at Walton and the North Downs recharge zone, the supply blend carries a high proportion of this chalk-dominated water, producing very hard water with TDS 655.3 mg/L.

At 251.5 mg/L, limescale is a significant and persistent household challenge in Chertsey. Kettles require descaling fortnightly to prevent element damage and calcium deposits in drinks. The combi-boiler needs a properly fitted scale inhibitor and annual professional servicing. Washing-up liquid requires considerably more product per wash to produce adequate lather. Taps, shower heads, and basin mixers develop heavy limescale deposits within one to two weeks; a fortnightly descaling wipe with white vinegar or a proprietary product is strongly advisable. A whole-house water softener is strongly recommended to protect all appliances, plumbing, and the boiler in this very hard Thames chalk supply town.