South East Water Tap Water Quality

South East Water supplies Kent & Sussex with drinking water drawn from chalk aquifers of the North Downs and Wealden greensand, plus surface water from local reservoirs.

South East Water serves Kent and Sussex — a region with diverse geology but predominantly chalk and greensand aquifers that produce hard to very hard water. Zones along the North Downs chalk scarp (Maidstone, Tonbridge) typically see hardness of 250–300 mg/L. Coastal and Weald zones drawing from greensand and river sources are moderately hard at 150–220 mg/L. The company has historically faced challenges with nitrate in some chalk groundwater sources, and has active investigations related to PFAS contamination near former industrial and military sites in Kent.

Typical water profile

With typical hardness of approximately 240 mg/L CaCO₃, water in the South East Water supply area is classified as hard to very hard. This means significant limescale buildup on kettles, showerheads, and heating elements over time. A water softener or quality filter jug is a worthwhile investment for most households in this area.

Notable: Hard to very hard water across most zones. Some elevated nitrates in chalk groundwater. Active PFAS programme under DWI enforcement.

Is South East Water water safe to drink?

Yes. All treated water supplied by South East Water meets the UK Drinking Water Regulations. The Drinking Water Inspectorate (DWI) audits every water company annually — South East Water serves 2.2 million customers across 36 supply zones. Each zone is tested thousands of times per year and results are published in the annual compliance report.

However, water quality varies significantly between zones within the South East Water supply area. Your specific zone may have different hardness, nitrate, or THM levels from your neighbour in a different zone. That's why it's worth checking your exact postcode above.

How to check your South East Water zone

Enter your postcode in the box above to see zone-specific data for your address — including hardness, nitrates, lead, chlorine, fluoride, and THMs — drawn directly from South East Water's most recent annual compliance report.