How to read a UK tap-water quality report
Read the location, reporting period and sampling details before interpreting a number. A supply-area report is useful evidence, but cannot certify the water at every tap today.
Begin with the scope
Check the supplier and named supply zone. A postcode can cover multiple supplies; an administrative ward is not a water zone. Then find the sample period. The date a website downloaded a report is not the date the water was tested.
Read the complete result
Keep the parameter name, units, mean, sample count, range and any less-than symbol together. For example, “<0.67 µg/l” is a reported upper detection bound, not an exact concentration of 0.67. A missing value means unavailable, not zero. A mean below a reference limit does not demonstrate that every sample complied.
Check investigations and current advice
Read reported contraventions alongside the supplier’s explanation and actions. Some investigations relate to plumbing at individual properties. National compliance statistics describe a wider population, not your address. If appearance, taste or smell changes now, follow current supplier advice; the annual average cannot diagnose that change.
Related questions
Hardness unit converter · Understand a supplier report
Check your published area information
Sources and review
Sources checked 6 September 2026. Prepared by WaterGrade.
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