UK Legal Limit
0 per 100ml
WHO Guideline
0 per 100ml
EU Standard
0 per 100ml
Primary Sources
Soil, sewage, pipe ingress
Coliform Bacteria in UK drinking water is regulated at 0 per 100ml. The WHO guideline is 0 per 100ml and the EU standard is 0 per 100ml. UK regulations require zero coliform bacteria in treated water. Detection indicates possible treatment failure and triggers immediate investigation.
Most coliform bacteria are not pathogenic and do not cause illness directly. However, their detection in treated drinking water is treated as a serious event because it signals that the water may have been exposed to faecal contamination or that the treatment barrier has been compromised. This means that harmful organisms — including E. coli, Cryptosporidium, and viruses — could also be present. When coliforms are detected, water companies must investigate immediately and may issue precautionary boil-water notices.
Coliform bacteria are found naturally in soil, vegetation, and the intestines of warm-blooded animals. They enter water sources through agricultural runoff, sewage discharges, and surface water contamination. In treated water, coliform detection usually points to a breakdown in the treatment process, inadequate disinfection, ingress of contaminated water into the distribution network through cracked pipes, or regrowth in biofilms within the pipe system. Warm weather and stagnant water can promote bacterial growth.
| Jurisdiction | Limit / Guideline | Notes |
|---|---|---|
| UK (DWI) | 0 per 100ml | Regulated under the Water Supply (Water Quality) Regulations 2016 |
| WHO | 0 per 100ml | World Health Organization Guidelines for Drinking-water Quality |
| EU | 0 per 100ml | EU Drinking Water Directive (2020/2184). The UK no longer automatically mirrors EU standards post-Brexit. |
UV disinfection
Ultraviolet light at 254nm wavelength damages the DNA of bacteria and viruses, preventing them from reproducing. Highly effective against microorganisms without adding chemicals to the water.
Reverse osmosis
A membrane filtration process that removes up to 99% of contaminants by forcing water through a semi-permeable membrane under pressure. Highly effective but produces some wastewater.
Chlorination
Adding chlorine or chloramine to water kills bacteria and viruses. The standard disinfection method used by UK water companies. Effective against E. coli and most waterborne pathogens.
No filter we list names coliform bacteria specifically. Reverse osmosis is shown because it rejects dissolved contaminants broadly rather than by name. Check your own report before buying.
Waterdrop G3P600 Reverse Osmosis
Reverse Osmosis · NSF/ANSI 58, NSF/ANSI 372
Typical price
£550approx.
Affiliate link: we may earn a commission at no extra cost to you.
Waterdrop 10UA Under Sink
Under-Sink Filter · NSF/ANSI 42
Typical price
£75approx.
Affiliate link: we may earn a commission at no extra cost to you.
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