Cheam Water Hardness & Quality Report (2026)

Sutton and East Surrey Water provides service to Cheam and other areas in Greater London and Surrey, such as Sutton, Morden, Epsom, and Ewell. Unlike neighboring Thames Water, which draws from surface rivers, SES Water primarily sources its supply from underground aquifers. The main treatment facility is the Cheam Water Treatment Works. This facility recently experienced a significant valve failure, which led to interruptions in service and the establishment of distribution points for bottled water. SES Water manages reserve supplies and has contingency plans in place to ensure the reliability of its suburban water network. The watershed area includes the North Downs, a chalk ridge in Surrey, which feeds the underground Chalk aquifer.

The Chalk Group rocks, specifically the Upper and Middle Chalk formations, act as the main reservoirs and pathways for the water. Overlying Palaeogene clays restrict direct connections with the surface. This geological makeup, characterized by porous limestone, naturally dissolves minerals, resulting in a characteristically hard water supply with elevated bicarbonate levels. This level of mineralization is typical for groundwater found in southeastern England. Rainfall replenishes the aquifer across the Downs, influencing the water's chemical composition without direct input from rivers.

Homeowners in this region will likely notice limescale deposits forming in appliances like kettles, boilers, and showerheads, which can decrease their efficiency and necessitate frequent cleaning. The lifespan of dishwashers, washing machines, and hot water systems may be shortened, and their energy consumption could increase. Routine maintenance, such as flushing with vinegar or using commercial descaling products, can help manage this buildup. For households dealing with consistently hard water, installing a water softener is often advised to protect appliances and improve the lathering of soaps and detergents, though it's worth noting that this process adds sodium to the water. SES Water treats the groundwater at Cheam Works using methods like aeration, filtration, and disinfection to meet regulatory standards.