Best and worst tap water in the UK
Rankings based on 2241 postcode areas tested. Scores reflect contaminant levels, PFAS, and overall water quality from real drinking water tests and environmental monitoring.
As of 2026, SA36 (Pembrokeshire) has the best tap water quality in the UK with a score of 10.0/10, while CO14 (Tendring) scores lowest at 0.0/10. Rankings are based on 2241 postcode districts tested for 100+ contaminants including lead, PFAS, nitrate, and trihalomethanes.
Top 10 cleanest
The highest-scoring areas in the UK.
1.SA36Pembrokeshire
Dŵr Cymru Welsh Water
10.0/10
2.S20Sheffield
Yorkshire Water
10.0/10
3.CH4Flintshire
Dŵr Cymru Welsh Water
10.0/10
4.CF30Cardiff
Dŵr Cymru Welsh Water
10.0/10
5.BS37South Gloucestershire
Bristol Water
9.9/10
6.TS9North Yorkshire
Yorkshire Water
9.8/10
7.TN40Rother
Southern Water
9.8/10
8.TN26Ashford
Southern Water
9.8/10
9.SP6New Forest
Southern Water
9.8/10
10.NE48Northumberland
Northumbrian Water
9.8/10
Top 10 worst
The lowest-scoring areas in the UK.
1.CO14Tendring
Anglian Water1 flagged
0.0/10
2.TQ1Torbay
Unknown1 flagged
0.0/10
3.IG7Redbridge
Thames Water2 flagged
2.9/10
4.SS3Southend-on-Sea
Anglian Water3 flagged
3.6/10
5.HP9Buckinghamshire
Thames Water3 flagged
4.5/10
6.SS8Castle Point
Anglian Water5 flagged
4.5/10
7.TN30Ashford
Southern Water
4.5/10
8.CB11Uttlesford
Anglian Water3 flagged
4.6/10
9.SS16Basildon
Anglian Water3 flagged
4.6/10
10.BH19Dorset
Wessex Water3 flagged
4.8/10
By water company
Average postcode safety score per supplier — not compliance rate.
#SupplierAvg safety scorePostcodes
1United Utilities9.52Dŵr Cymru Welsh Water9.53Northumbrian Water9.54South West Water9.45Yorkshire Water9.36Severn Trent9.17Affinity Water9.18Southern Water9.09Bristol Water8.910Anglian Water8.911Scottish Water8.812Wessex Water8.613Portsmouth Water8.514Thames Water8.415South East Water8.316Unknown7.1Check your postcode
See exactly what's in the tap water at your address.
Compare two cities
Side-by-side water quality for the UK's largest cities, based on the same test data as the postcode reports.
London vs ManchesterLondon vs BirminghamLondon vs LeedsLondon vs GlasgowLondon vs EdinburghLondon vs BristolLondon vs LiverpoolLondon vs SheffieldLondon vs NottinghamLondon vs CardiffManchester vs BirminghamManchester vs LeedsManchester vs LiverpoolManchester vs SheffieldManchester vs GlasgowBirmingham vs LeedsBirmingham vs BristolBirmingham vs NottinghamEdinburgh vs GlasgowLeeds vs SheffieldBristol vs CardiffLiverpool vs LeedsNewcastle vs SunderlandNottingham vs Leicester