Mortlake Water Hardness & Quality Report (2026)

Thames Water supplies Mortlake in Greater London with treated water. The primary source is river abstraction from the Thames Valley, with water undergoing treatment at the Richmond Treatment Works before it reaches residents. Thames Water manages a vast network, drawing from both surface and groundwater across the London and Thames Valley regions. Mortlake's water profile is significantly influenced by the watershed characteristics of South East England and the geology of the Cretaceous Chalk Formation.

The region's underlying geology, characterized by chalk and limestone deposits within the London Basin, plays a crucial role in the water's composition. As water naturally percolates through these formations and flows over them, it dissolves significant amounts of minerals, primarily calcium and magnesium carbonates. This geological interaction is the direct cause of the supply's high mineral content and its classification as hard water.

Homeowners in Mortlake often notice the effects of this hard water, with limescale buildup being a common issue on fixtures, in kettles, and within appliances like water heaters and dishwashers. To combat scale accumulation and maintain the efficiency of these devices, many residents opt for water softeners or use anti-limescale treatments. Regular descaling of appliances is also advised. Despite its hardness, the tap water provided by Thames Water is perfectly safe to drink, adhering strictly to the standards set by the UK Drinking Water Inspectorate.