Best and worst tap water in the UK
Rankings based on 2245 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 2245 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.S20Rotherham
Yorkshire Water
10.0/10
3.CH4Cheshire West and Chester
United Utilities
10.0/10
4.CF30Cardiff
Dŵr Cymru Welsh Water
10.0/10
5.SP6Dorset
Wessex Water
9.9/10
6.RG21Basingstoke and Deane
Southern Water
9.9/10
7.GU51Hart
Southern Water
9.9/10
8.BS7Bristol, City of
Bristol Water
9.9/10
9.YO16East Riding of Yorkshire
Yorkshire Water
9.8/10
10.WV12Walsall
Severn Trent
9.8/10
Top 10 worst
The lowest-scoring areas in the UK.
1.CO14Tendring
Anglian Water1 flagged
0.0/10
2.DA13Dartford
Thames Water6 flagged
5.2/10
3.BS11Bristol, City of
Bristol Water4 flagged
5.6/10
4.BS9Bristol, City of
Bristol Water2 flagged
5.6/10
5.SS16Basildon
Anglian Water5 flagged
5.7/10
6.SS3Rochford
Anglian Water4 flagged
5.7/10
7.BS25North Somerset
Bristol Water1 flagged
6.3/10
8.BS41Bath and North East Somerset
Wessex Water4 flagged
6.7/10
9.ME6Tonbridge and Malling
Southern Water
6.9/10
10.BA4Somerset
Wessex Water2 flagged
7.0/10
By water company
Average postcode safety score per supplier — not compliance rate.
#SupplierAvg safety scorePostcodes
1Dŵr Cymru Welsh Water9.52United Utilities9.53Yorkshire Water9.54Scottish Water9.45South West Water9.46Northumbrian Water9.47Severn Trent9.28Southern Water9.19Anglian Water9.010Affinity Water9.011Wessex Water8.912South East Water8.913Bristol Water8.914Thames Water8.515Portsmouth Water8.516Unknown8.4Check your postcode
See exactly what's in the tap water at your address.