2026 Data
UK's Worst Tap Water: Lowest Rated Postcodes
The UK postcodes with the lowest water quality scores. Ranked by TapWater.uk safety score.
According to TapWater.uk's analysis of 1,942 UK postcodes, the lowest-scoring postcode recorded 7.0/10.
7.0
Lowest score
9.1
UK average
Top 50 postcodes
Ranked by lowest safety score. Click any postcode for a full report.
Scores are based on 1,942 postcode districts with Environment Agency data. Score methodology: contaminant levels measured against UK legal limits and WHO guidelines.
What this means
A low safety score does not mean water is unsafe to drink. All UK tap water meets legal standards enforced by the Drinking Water Inspectorate. Low scores indicate that contaminant levels are closer to legal limits or exceed stricter WHO advisory guidelines. They highlight areas where water quality could be improved.
How to protect yourself
A reverse osmosis system provides the most comprehensive filtration, removing lead, nitrate, PFAS, pesticides, and other contaminants. For specific concerns, check your postcode page to see which contaminants are elevated.
Check your postcode
See the full water quality report for your area, including all tested contaminants and personalised filter recommendations.
Frequently asked questions
Is UK tap water safe to drink even with a low score?
Yes. All UK tap water must meet legal safety standards set by the Drinking Water Inspectorate. A low score on TapWater.uk does not mean water is unsafe — it means more contaminants were detected at levels closer to legal limits, or above stricter WHO guidelines. The UK has some of the most regulated tap water in the world.
Why does my area have a low water quality score?
Low scores can result from several factors: proximity to agricultural land (higher nitrate/pesticide levels), old infrastructure (lead pipes), industrial or military sites (PFAS), or naturally hard water. Multiple contaminants near their respective limits will also lower the overall score.
What should I do if my area has a low water quality score?
Consider installing a water filter appropriate to your area's specific concerns. Check the contaminant breakdown on your postcode page to see what is driving the low score. For lead concerns, contact your water company about pipe replacement. For a general solution, a reverse osmosis filter removes the widest range of contaminants.
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Highest Lead Levels
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Highest Nitrate Levels
Nitrate levels by UK postcode. Data from Environment Agency and water company testing.
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PFAS Detections
Which UK postcodes have PFAS forever chemicals in nearby water sources? Environment Agency monitoring data.
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Hardest Water
The UK postcodes with the hardest water. Ranked by calcium carbonate levels.
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Best Water Quality
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