Which UK city has the best tap water?

Middlesbrough has the best tap water quality of all 51 major UK cities, with an average safety score of 9.6/10 across 15 postcode districts tested. Data is sourced from the Environment Agency.

Which UK city has the worst tap water?

London has the lowest water quality score of the cities ranked, with an average safety score of 8.3/10 across 58 postcode districts. All UK tap water meets legal safety standards — lower scores reflect elevated contaminant levels relative to WHO guidelines.

Which water company has the best water?

Northumbrian Water ranks as the top-performing water supplier with an average safety score of 9.5/10 across 117 postcode districts served. Rankings are based on Environment Agency and water company testing data.

How are the water quality rankings calculated?

Rankings are based on Environment Agency water quality monitoring data. Each postcode district receives a safety score from 0–10 based on contaminant levels measured against UK legal limits and WHO guidelines. City and supplier scores are weighted averages across all postcode districts with data. Lower scores indicate more contaminants exceeding recommended thresholds — not that water is unsafe to drink.

UK Water Quality Rankings

Based on 2,245 postcode districts tested. Last updated 30 September 2026. How scores are calculated

Cities ranked44
Water companies18
Regions10
Areas tested2,245

Best & worst cities

The cities with the highest and lowest average water quality scores in the UK.

Top 5 — Cleanest water

Middlesbrough9.6/10

England · 15 areas tested

Bradford9.6/10

England · 21 areas tested

Swansea9.6/10

Wales · 7 areas tested

Sheffield9.5/10

England · 17 areas tested

Sunderland9.5/10

England · 10 areas tested

Bottom 5 — Areas to watch

#40

London8.3/10

England · 58 areas tested

#41

Portsmouth8.5/10

England · 6 areas tested

#42

Reading8.5/10

England · 17 areas tested

#43

Swindon8.5/10

England · 8 areas tested

#44

Oxford8.5/10

England · 14 areas tested

All cities ranked

44 cities, ranked by average water quality score. Click any city for a detailed breakdown.

#CityScoreIssues flaggedPFASMain supplier

MiddlesbroughEngland

9.6/100—Northumbrian Water 2

BradfordEngland

9.6/100—Yorkshire Water 3

SwanseaWales

9.6/100—Dŵr Cymru Welsh Water 4

SheffieldEngland

9.5/100—Yorkshire Water 5

SunderlandEngland

9.5/100—Northumbrian Water 6

PlymouthEngland

9.5/100—South West Water 7

HuddersfieldEngland

9.5/100—Yorkshire Water 8

LeedsEngland

9.5/100—Yorkshire Water 9

CardiffWales

9.5/100—Dŵr Cymru Welsh Water 10

WiganEngland

9.4/100—United Utilities 11

ManchesterEngland

9.4/100—United Utilities 12

BlackburnEngland

9.4/100—United Utilities 13

StockportEngland

9.4/100—United Utilities 14

Stoke-on-TrentEngland

9.4/100—Severn Trent 15

NewcastleEngland

9.4/100—Northumbrian Water 16

ExeterEngland

9.3/100—South West Water 17

LiverpoolEngland

9.3/100—United Utilities 18

WarringtonEngland

9.3/100—United Utilities 19

BrightonEngland

9.3/104—Southern Water 20

GloucesterEngland

9.3/100—Severn Trent 21

NorthamptonEngland

9.3/101—Anglian Water 22

BlackpoolEngland

9.2/101—United Utilities 23

BirminghamEngland

9.2/100—Severn Trent 24

PrestonEngland

9.2/102—United Utilities 25

IpswichEngland

9.1/101—Anglian Water 26

DerbyEngland

9.1/100—Severn Trent 27

NottinghamEngland

9.1/100—Severn Trent 28

CheltenhamEngland

9.1/101—Severn Trent 29

NorwichEngland

9.1/100—Anglian Water 30

SouthamptonEngland

9.1/1091Southern Water 31

YorkEngland

9.0/103—Yorkshire Water 32

CambridgeEngland

9.0/108—Cambridge Water 33

LincolnEngland

9.0/100—Anglian Water 34

LeicesterEngland

8.9/100—Severn Trent 35

HullEngland

8.9/1027—Yorkshire Water 36

WolverhamptonEngland

8.8/102—Severn Trent 37

BristolEngland

8.7/1012Bristol Water 38

BathEngland

8.7/1012Wessex Water 39

CoventryEngland

8.6/100—Severn Trent 40

OxfordEngland

8.5/1014—Thames Water 41

SwindonEngland

8.5/108—Thames Water 42

ReadingEngland

8.5/10171Thames Water 43

PortsmouthEngland

8.5/104—Portsmouth Water 44

LondonEngland

8.3/1079—Thames Water

Score is average across all postcode districts in each city. PFAS column shows number of postcode districts where forever chemicals were detected.

Water company leaderboard

18 water companies ranked by average safety score across all postcodes served.

#CompanyAvg scoreAreas served

Northumbrian Water

9.5

117 2

Dŵr Cymru Welsh Water

30 8

9 9

Essex & Suffolk Water

4 14

6 16

Only companies serving 2 or more postcode districts are shown. Score is the unweighted average across all postcodes in the supplier's coverage area.

Regional comparison

10 regions ranked by average water quality score.

North East England

3 cities · 34 areas

9.5

/10

Wales

2 cities · 16 areas

9.5

/10

North West England

4 cities · 65 areas

9.3

/10

Yorkshire and the Humber

5 cities · 102 areas

9.3

/10

West Midlands

4 cities · 68 areas

9.1

/10

East Midlands

3 cities · 24 areas

9.1

/10

East of England

3 cities · 23 areas

9.1

/10

South West England

4 cities · 39 areas

8.9

/10

South East England

3 cities · 19 areas

8.9

/10

#10

London

1 cities · 58 areas

8.3

/10

How these rankings work

Rankings are based on water quality monitoring data from the Environment Agency Water Quality Archive and water company testing via the Stream Water Data Portal. Each postcode district receives a safety score from 0–10 based on measured contaminant levels against UK legal limits and WHO guidelines. City, supplier, and regional scores are averages across all postcode districts with data.

A lower score does not mean water is unsafe — all UK tap water meets legal standards. Scores reflect how cleanly water performs relative to both mandatory UK limits and stricter WHO advisory guidelines. PFAS detections are flagged where detected, even though the UK has no legal limit for PFAS in drinking water.

Read the full methodology