Can I Drink Tap Water in London?

London's tap water is supplied by Thames Water, which serves 76% of Greater London's population. The water is sourced primarily from the River Thames and the River Lea, both surface reservoirs. It undergoes advanced multi-stage treatment including screening, storage and settlement, flocculation, sand filtration, ozonation, activated carbon filtration, and final chlorine disinfection. More than 99.96% of samples taken from customer taps meet the strict standards set by UK legislation and the EU Drinking Water Directive. The Drinking Water Inspectorate (DWI) independently regulates and audits all water companies in England and Wales.

London's drinking water originates from surface reservoirs fed by the River Thames near Heathrow and the River Lea in North London, with approximately 30% supplemented from underground chalk and gravel aquifers. Thames Water operates multiple treatment works across the capital, including major facilities at Walton, Hampton, and Kempton Park. The treatment process begins with coarse screening to remove debris, followed by storage in reservoirs where natural settlement occurs. Water then passes through flocculation and clarification to remove fine particles, sand filtration, and at many works, ozonation and granular activated carbon filtration to remove pesticides, organic compounds, and taste and odour. A small residual dose of chlorine (less than 1 mg/L) is added as final disinfection to protect water through the distribution network. London's water is classified as very hard, averaging 293 mg/L as calcium carbonate, due to the chalk and limestone geology of South East England. This hardness causes limescale buildup in kettles and pipes but poses no health risk and provides dietary calcium and magnesium. The TDS (Total Dissolved Solids) averages around 316 mg/L. An Imperial College London study in 2024 detected trace PFAS (per- and polyfluoroalkyl substances) in London tap water at concentrations of 3-8 nanograms per litre, well below the DWI's lowest-risk threshold of 10 ng/L per individual compound. The CDC classifies UK tap water as safe for travellers with no special precautions required.

Visitors to London can drink tap water with complete confidence. The water meets all WHO, EU, and UK safety standards and requires no filtering, boiling, or special treatment. Ice in drinks, water at restaurants, and tap water at hotels are all safe. The high mineral content may taste different from what you are accustomed to but is entirely safe. Bottled water is available everywhere but is unnecessary for health reasons.