Affinity Water Tap Water Quality

Affinity Water supplies South East England with drinking water drawn from chalk and Chalk Marl aquifers of the Chilterns, North London chalk, and some River Lee and River Colne abstractions.

Affinity Water supplies a wide arc of territory north and east of London, almost entirely underlain by chalk. This produces some of the hardest water in the UK — typical hardness across the supply area runs 280–340 mg/L CaCO₃, with zones in Hertfordshire and the Chilterns regularly exceeding 320 mg/L. Luton, St Albans, and Watford are among the hardest-water towns in the country. Nitrate is a key parameter: agricultural pressure on chalk aquifers has elevated nitrate in several zones to 30–45 mg/L, approaching but remaining within the 50 mg/L legal limit. Several active DWI investigations relate to nitrate management and PFAS.

Typical water profile

With typical hardness of approximately 310 mg/L CaCO₃, water in the Affinity Water supply area is classified as 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: Very hard water throughout the supply area (avg ~310 mg/L). Elevated nitrates in some chalk groundwater zones. Lead compliance monitored closely. Active PFAS notice — multiple zones under DWI investigation.

Is Affinity Water water safe to drink?

Yes. All treated water supplied by Affinity Water meets the UK Drinking Water Regulations. The Drinking Water Inspectorate (DWI) audits every water company annually — Affinity Water serves 3.6 million customers across 92 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 Affinity 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 Affinity 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 Affinity Water's most recent annual compliance report.