Bexley Water Hardness & Quality Report (2026)

Bexley, a South East London borough bordering the River Thames at the Cray valley, receives its water from Thames Water. Supply is drawn from the Lee Valley Reservoir Chain — including King George V Reservoir and William Girling Reservoir — and from the Thames Valley Reservoir Group to the south-west. The Lee Valley sources receive water abstracted from the chalk-fed River Lee in Hertfordshire, while Thames abstractions carry dissolved minerals from Cotswold and chalk upstream catchments. Water is treated at Coppermills Water Treatment Works in Walthamstow and Thames-side treatment works before distribution through the South East London network to Bexley and the wider borough.

Bexley's hardness of 268 mg/L (18.8°Clark) reflects its position within Thames Water's hard-water supply network. The Thames Basin Chalk underlying South East London and Kent is the same continuous Cretaceous chalk that produces the South Downs springs. The River Lee, a primary source, flows almost entirely through chalk countryside from its Hertfordshire headwaters. Surface water from the Thames upstream carries dissolved calcium from the Chalk, Greensand, and Jurassic limestone beds of Oxfordshire and Berkshire. Bexley's supply, blended from these chalk-influenced sources, places it firmly in the hard band of the Drinking Water Inspectorate (DWI) classification.

Limescale is a consistent feature of Bexley homes. At 268 mg/L, limescale accumulates quickly — kettles need descaling every two to three weeks, and monthly use of a proprietary descaler is standard. Combi-boilers are at significant risk of heat exchanger limescale if unprotected — annual boiler servicing with a limescale inspection is essential, and an in-line scale inhibitor is strongly recommended. Showerheads, taps, and glass shower screens develop heavy limescale deposits requiring regular removal. Washing-up liquid lathers very poorly. Bexley homeowners with hard-water-sensitive appliances should consider fitting a magnetic conditioner or water softener for effective long-term limescale management.