New Malden Water Hardness & Quality Report (2026)

New Malden, the south-west London neighbourhood in the London Borough of Kingston upon Thames between Kingston, Wimbledon and Raynes Park — notable as the heart of Korean community life in Britain — is supplied by Thames Water predominantly from the River Thames abstraction at Hampton Water Treatment Works. Hampton WTW is one of Europe's largest water treatment facilities, processing vast quantities of Thames river water daily. New Malden's supply zone draws heavily on this Hampton Thames surface-water treatment rather than on deep chalk borehole water, producing a supply at 187 mg/L that is very similar in hardness to Sunbury-on-Thames (186.5 mg/L) and New Milton (297 mg/L) but softer than chalk-borehole-dominant zones such as Isleworth (282 mg/L) nearby. The TDS of 411.8 mg/L — with a relatively low TDS-to-hardness ratio of 2.20 — confirms a predominantly Thames surface-water supply character, with limited deep chalk borehole water contribution.

The River Thames at Hampton carries chalk-influenced water from its upper chalk and Cotswold limestone catchment, but is substantially diluted by non-chalk tributaries including the Mole, Wey and Kennet lower catchments. By the time Thames water reaches Hampton WTW the hardness is 180–200 mg/L — harder than northern English rivers but softer than pure chalk borehole groundwater. This Thames-surface-water-dominant supply character in New Malden's distribution zone produces a consistently moderate hardness that tracks the Thames river water chemistry rather than the more extreme chalk borehole character of outer south-west London.

At 187 mg/L New Malden's water is moderately hard and limescale management is a steady routine. Kettles benefit from descaling every four to six weeks. Shower screens develop moderate calcium spotting that responds to regular white vinegar cleaning. Washing-up liquid lathers adequately with moderate amounts. Combi-boilers benefit from inline scale inhibitor protection. New Malden's cosmopolitan character and Korean restaurant district have helped transform south-west London — and its moderately hard Thames river water is the characteristic supply of the entire Kingston-upon-Thames stretch of the south bank.