Best and worst tap water in the UK
Rankings based on 1168 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 DA12 (Gravesham) scores lowest at 5.1/10. Rankings are based on 1168 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.CF30Cardiff
Dŵr Cymru Welsh Water
10.0/10
3.CA12Cumberland
Unknown
10.0/10
4.GU51Hart
Unknown
9.9/10
5.BS7Bristol, City of
Bristol Water
9.9/10
6.BD23North Yorkshire
Unknown
9.9/10
7.SY12Shropshire
Severn Trent
9.8/10
8.RG4South Oxfordshire
Thames Water
9.8/10
9.RG2Wokingham
Thames Water
9.8/10
10.NP25Herefordshire, County of
Unknown
9.8/10
Top 10 worst
The lowest-scoring areas in the UK.
1.DA12Gravesham
Southern Water6 flagged
5.1/10
2.DA13Gravesham
Southern Water6 flagged
5.2/10
3.DN8North Lincolnshire
Unknown3 flagged
5.3/10
4.RG6Wokingham
Thames Water2 flagged
5.5/10
5.BS11Bristol, City of
Bristol Water4 flagged
5.6/10
6.BS9Bristol, City of
Bristol Water2 flagged
5.6/10
7.NG2Gedling
Severn Trent3 flagged
6.1/10
8.NG3Gedling
Severn Trent3 flagged
6.1/10
9.BS25North Somerset
Bristol Water1 flagged
6.3/10
10.N22Enfield
Thames Water1 flagged
6.5/10
By water company
Average water quality scores ranked by supplier.
#SupplierAvg scoreAreas
1Dŵr Cymru Welsh Water9.52Scottish Water9.43Yorkshire Water9.34South West Water9.35Affinity Water9.16South East Water9.17NI Water9.18Severn Trent9.19United Utilities9.110Southern Water9.011Unknown8.912Anglian Water8.913Bristol Water8.914Wessex Water8.815Northumbrian Water8.716Thames Water8.517Portsmouth Water8.5Check your postcode
See exactly what's in the tap water at your address.