Is London tap water safe to drink?

Who supplies water in London

Drinking-water test record

How hard is the water in London?

Storm overflows nearby

Older homes and lead pipes

Fluoride

Hosepipe bans

What you can do

Common water problems

• How much does a water softener cost in the UK?

  Water softener cost UK 2026: price by home size

• Why is my tap water cloudy or white?

  Why is my tap water cloudy or white? (UK)

• Why is my tap water brown?

  Brown tap water: causes and what to do (UK)

• Why does my tap water taste metallic?

  Tap water tastes metallic? Causes and fixes (UK)

Questions about tap water in London

Is the water in London hard or soft?

Thames Water: “all the water in our region is hard” (Thames Water, Thames Water, company-wide, read on 26 September 2026). SES Water: We do not have a verified hardness figure for this area. Ask your water company for its water quality report. Affinity Water: very hard, 352 mg/l, 24.7 °Clark, 19.7 °dH, 35.2 °fH (Stanmore/Mill Hill (supply zone), read on 29 September 2026). From the company's postcode lookup. Affinity Water: hard, 271 mg/l, 19.0 °Clark, 15.2 °dH, 27.1 °fH (East Barnet (supply zone), read on 29 September 2026). From the company's postcode lookup. Affinity Water: very hard, 331 mg/l, 23.2 °Clark, 18.5 °dH, 33.1 °fH (Colindale/Kingsbury (supply zone), read on 29 September 2026). From the company's postcode lookup. Essex & Suffolk Water: We do not have a verified hardness figure for this area. Ask your water company for its water quality report. Affinity Water: hard, 275 mg/l, 19.3 °Clark, 15.4 °dH, 27.5 °fH (Finchley (supply zone), 1 January 2025 to 31 December 2025). Zone average. Essex & Suffolk Water: hard, 281 mg/l, 19.7 °Clark, 15.7 °dH, 28.1 °fH (ROMFORD WEST (supply zone), January 2025 to December 2025). Zone average. Affinity Water: very hard, 310 mg/l, 21.7 °Clark, 17.4 °dH, 31.0 °fH (Edgware (supply zone), 1 January 2025 to 31 December 2025). Zone average. Affinity Water: very hard, 321 mg/l, 22.5 °Clark, 18.0 °dH, 32.1 °fH (Ruislip (supply zone), read on 28 September 2026). From the company's postcode lookup. Affinity Water: hard, 295 mg/l, 20.7 °Clark, 16.5 °dH, 29.5 °fH (Barnet (supply zone), 1 January 2025 to 31 December 2025). Zone average. Essex & Suffolk Water: hard, 247 mg/l, 17.3 °Clark, 13.8 °dH, 24.7 °fH (ROMFORD EAST (supply zone), January 2025 to December 2025). Zone average. Affinity Water: very hard, 361 mg/l, 25.3 °Clark, 20.2 °dH, 36.1 °fH (Harrow North (supply zone), read on 28 September 2026). From the company's postcode lookup. Affinity Water: hard, 267 mg/l, 18.7 °Clark, 15.0 °dH, 26.7 °fH (Rayners Lane (supply zone), read on 29 September 2026). From the company's postcode lookup. Essex & Suffolk Water: hard, 288 mg/l, 20.2 °Clark, 16.1 °dH, 28.8 °fH (DAGENHAM (supply zone), January 2025 to December 2025). Zone average. Affinity Water: hard, 295 mg/l, 20.7 °Clark, 16.5 °dH, 29.5 °fH (Wembley (supply zone), 1 January 2025 to 31 December 2025). Zone average. Affinity Water: hard, 279 mg/l, 19.6 °Clark, 15.6 °dH, 27.9 °fH (Southall (supply zone), read on 29 September 2026). From the company's postcode lookup. Essex & Suffolk Water: hard, 257 mg/l, 18.0 °Clark, 14.4 °dH, 25.7 °fH (HAROLD HILL (supply zone), January 2025 to December 2025). Zone average. Essex & Suffolk Water: hard, 242 mg/l, 17.0 °Clark, 13.6 °dH, 24.2 °fH (UPMINSTER (supply zone), January 2025 to December 2025). Zone average. Affinity Water: very hard, 306 mg/l, 21.5 °Clark, 17.1 °dH, 30.6 °fH (Uxbridge (supply zone), read on 29 September 2026). From the company's postcode lookup. Affinity Water: hard, 285 mg/l, 20.0 °Clark, 16.0 °dH, 28.5 °fH (Ickenham/Denham (supply zone), 1 January 2025 to 31 December 2025). Zone average. Affinity Water: hard, 277 mg/l, 19.4 °Clark, 15.5 °dH, 27.7 °fH (Yeading (supply zone), read on 29 September 2026). From the company's postcode lookup. Affinity Water: very hard, 304 mg/l, 21.3 °Clark, 17.0 °dH, 30.4 °fH (Greenford/Northolt (supply zone), read on 29 September 2026). From the company's postcode lookup. Affinity Water: very hard, 363 mg/l, 25.5 °Clark, 20.3 °dH, 36.3 °fH (Harrow South (supply zone), 1 January 2025 to 31 December 2025). Zone average. Affinity Water: hard, 300 mg/l, 21.0 °Clark, 16.8 °dH, 30.0 °fH (West Drayton (supply zone), read on 29 September 2026). From the company's postcode lookup. Essex & Suffolk Water: hard, 280 mg/l, 19.6 °Clark, 15.7 °dH, 28.0 °fH (HORNCHURCH (supply zone), January 2025 to December 2025). Zone average. Affinity Water: hard, 265 mg/l, 18.6 °Clark, 14.8 °dH, 26.5 °fH (Hayes (supply zone), 1 January 2025 to 31 December 2025). Zone average. Affinity Water: very hard, 346 mg/l, 24.3 °Clark, 19.4 °dH, 34.6 °fH (Belmont (supply zone), read on 29 September 2026). From the company's postcode lookup. Affinity Water: very hard, 348 mg/l, 24.4 °Clark, 19.5 °dH, 34.8 °fH (Northwood (supply zone), 1 January 2025 to 31 December 2025). Zone average. Affinity Water: hard, 277 mg/l, 19.4 °Clark, 15.5 °dH, 27.7 °fH (Feltham (supply zone), read on 29 September 2026). From the company's postcode lookup. Affinity Water: hard, 291 mg/l, 20.4 °Clark, 16.3 °dH, 29.1 °fH (Sudbury (supply zone), read on 29 September 2026). From the company's postcode lookup. Essex & Suffolk Water: hard, 296 mg/l, 20.8 °Clark, 16.6 °dH, 29.6 °fH (ILFORD (supply zone), January 2025 to December 2025). Zone average. Essex & Suffolk Water: hard, 296 mg/l, 20.8 °Clark, 16.6 °dH, 29.6 °fH (BARKINGSIDE (supply zone), January 2025 to December 2025). Zone average. Essex & Suffolk Water: hard, 295 mg/l, 20.7 °Clark, 16.5 °dH, 29.5 °fH (Seven Kings (supply zone), January 2025 to December 2025). Zone average. Affinity Water: very hard, 328 mg/l, 23.0 °Clark, 18.4 °dH, 32.8 °fH (Ashford (supply zone), 1 January 2025 to 31 December 2025). Zone average. Essex & Suffolk Water: hard, 265 mg/l, 18.6 °Clark, 14.9 °dH, 26.5 °fH (OCKENDON & STANFORD LE HOPE (supply zone), January 2025 to December 2025). Zone average. Affinity Water: hard, 282 mg/l, 19.8 °Clark, 15.8 °dH, 28.2 °fH (Rickmansworth/Gerrards Cross (supply zone), read on 29 September 2026). From the company's postcode lookup. SES Water: at least hard, at least 209 mg/l, at least 14.6 °Clark, at least 11.7 °dH, at least 20.9 °fH (How Green (supply zone), 2025 operational monitoring). Zone average. At least 209 mg/l (hard or harder); total hardness is higher. Affinity Water: very hard, 339 mg/l, 23.8 °Clark, 19.0 °dH, 33.9 °fH (Borehamwood/Bushey (supply zone), read on 29 September 2026). From the company's postcode lookup. Affinity Water: We do not have a verified hardness figure for this area. Ask your water company for its water quality report. Essex & Suffolk Water: hard, 249 mg/l, 17.5 °Clark, 14.0 °dH, 24.9 °fH (BILLERICAY & BRENTWOOD (supply zone), January 2025 to December 2025). Zone average. Affinity Water: hard, 279 mg/l, 19.6 °Clark, 15.6 °dH, 27.9 °fH (Hatfield/Potters Bar (supply zone), read on 29 September 2026). From the company's postcode lookup. SES Water: at least hard, at least 210 mg/l, at least 14.7 °Clark, at least 11.7 °dH, at least 21.0 °fH (Nork (supply zone), 2025 operational monitoring). Zone average. At least 210 mg/l (hard or harder); total hardness is higher.

What does the drinking water regulator's record show for London?

Thames Water: at least 68 tests failed UK drinking-water standards in 2025 (DWI, company-wide). Some published DWI figures don't reconcile or identify a company, so we've left them out; the true number may be higher. England overall: 99.97% of tests met standards.

Could homes in London have lead pipes?

69% of homes here were built before 1973 — estimate, not a test. Homes in the parts of London we can match to council-tax records (100% of its postcodes) whose build period is known; the share with no recorded build period isn't published for these areas. Allowing for suppressed counts: 67–69%. England and Wales: 61% (2026). Older homes are more likely to have lead pipes. Only a test tells you whether yours does.

Is the water in London fluoridated?

We cannot confirm whether this area is part of a water fluoridation scheme. Ask your water supplier using your postcode. Around one in ten people in England receive drinking water supplied by a fluoridation scheme.