Putney Water Hardness & Quality Report (2026)

Thames Water Utilities Limited supplies Putney in Greater London, drawing water from a combination of sources. Groundwater is abstracted from the London Basin Chalk aquifer via boreholes in the Lee Valley and near Staines. Surface water comes from the River Thames and reservoirs like Queen Mother Reservoir and Wraysbury Reservoir. Water is treated at major facilities including Hampton, Island, and Ashford Common works before distribution. The Thames Valley watershed, a key part of the supply area, includes inflows from the Colne and Lea rivers.

Geologically, the region is characterized by the Cretaceous Chalk Group, a porous limestone aquifer. This formation, often overlain by clay layers and Tertiary sands and gravels, allows rainwater to seep through and dissolve minerals. The karstic nature of this terrain, particularly in the North Downs and Chiltern Hills watersheds, naturally enriches the groundwater with calcium and magnesium. These dissolved minerals are the primary reason for the hard water supplied to residents in Putney and surrounding areas.

This very hard water commonly leads to limescale buildup in appliances such as kettles, boilers, and washing machines, which can reduce their efficiency and shorten their lifespan. Hot water systems and pipes are particularly susceptible to these chalky deposits. Homeowners often find regular descaling with vinegar and lowering boiler temperatures to 60°C helpful. Many residents opt to install a water softener to combat scale, prolong appliance life, and improve how soap lathers. Thames Water monitors pH levels, typically between 7.0-8.5, and complies with drinking water standards for lead and copper.