Unit of measurement
number/ 100ml
World Health Organisation Standards (1993)
Not mentioned
Standards for private water supplies in England (2016)
Standards for private water supplies in Scotland (2006)
Standards for private water supplies in Wales (2017)
European Union Drinking Water Directive (1998)


E.Coli, the shorthand term for Escherichia coli, is a gram-negative, rod-shaped type of faecal coliform bacteria. Commonly found in the intestines of warm-blooded animals and humans, the presence of any E.Coli bacteria in your drinking water is a strong indication that it has been recently contaminated with human sewage or animal waste.

This sewage or waste may have reached a drinking water source due to agricultural runoff and runoff from areas dirtied with pet manure, the water being part of varying wildlife's natural habitat, wastewater and sewage plants, and even heavy rain washing it into rivers, lakes and streams.

Whilst many strains of E.Coli are not a cause for concern, there are a few that have the capability to cause serious illness in humans and are even life-threatening; one of which being E.Coli (O157: H7). Afflictions which can be obtained from coming into contact with water contaminated with these harmful strains include gastrointestinal illness and infections of the skin, ears, eyes, respiratory and neurologic systems. What's more, E.Coli entering into a wound, such as may happen using contaminated water to take a shower or bath, can cause the wound to become infected. The most widely reported symptoms of drinking contaminated water, however, are stomach cramps, diarrhoea, sickness, and fever.

E.Coli found to be present in drinking water can also be used as an indicator to monitor a variety of other microbes which can be even more harmful such as the norovirus, Cryptosporidium, Giardia and Shigella.

When water is found to contain E.Coli, the recommendation is always that an alternative source of drinking water is used until such time as adequate and correct treatment of the drinking water can be carried out. Fortunately, E.Coli is not too difficult to eradicate and there are a few water treatment methods that can be used. The first is to use chlorine to disinfect the water and kill the bacteria. The second most common way to rectify E.Coli contamination is through the use of a UV filtration system. When the water passes through such a system bacteria is hit by UV light which kills it. These systems are generally favoured as they are efficient, easy to maintain, and do not require the addition of any chemical into the water.

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