What's in UK tap water?
UK water companies test for over 100 regulated parameters. These are the contaminants that matter most — what they are, where they come from, and whether your water is affected.
PFAS (Forever Chemicals)
No UK legal limit
Man-made chemicals that don't break down. Linked to cancer, immune disruption, and thyroid problems. The UK has no legal limit despite EU and WHO guidelines.
Lead
UK limit: 0.01 mg/L
Neurotoxin with no safe exposure level. Mainly from old pipes in pre-1970 homes. Affects children's cognitive development even at low levels.
Trihalomethanes (THMs)
UK limit: 0.1 mg/L
Disinfection byproducts formed when chlorine reacts with organic matter. Linked to bladder cancer risk. Higher in areas using surface water.
Nitrate
UK limit: 50 mg/L
From agricultural fertiliser runoff. Dangerous for infants under 3 months (blue baby syndrome). Elevated in farming regions.
E. coli
Zero tolerance
Indicator of faecal contamination. Any detection in treated water triggers immediate investigation. UK regulation requires zero presence.
Fluoride
UK limit: 1.5 mg/L
Added to ~10% of English water supplies. Prevents tooth decay but excess causes dental fluorosis. Naturally present in some regions.
Chlorine
UK limit: 5 mg/L (residual)
Added as disinfectant to kill bacteria. Safe at UK levels but creates byproducts (THMs). Can affect taste and smell.
Copper
UK limit: 2 mg/L
Mainly from copper plumbing. High levels cause nausea and stomach cramps. More common in new-build properties with soft water.
Check your area
Enter your postcode to see which contaminants have been detected in your local water supply, with real test results from your water company.
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