Boiling tap water for drinking purposes is not necessary in the United Kingdom, however, in certain cases, water companies or local authorities may issue boil water notices for a limited period of time instructing people to boil their water before consumption. Most commonly, boil water advisories are issued because of parasitic bug outbreaks. Indeed, microbial pathogens are the main culprits that prompt water companies to advise consumers to boil their water before using it for drinking or preparing food.

Outbreaks caused by high levels of Cryptosporidium, E. Coli and Giardia found in tap are perhaps the most common reasons why tap water becomes unfit for drinking without being boiled first. These outbreaks may not be frequent, but when they do occur, they affect hundreds of thousands of households, and sometimes, the notice to boil water can last for even two weeks like in the case of a Cryptosporidium outbreak in August 2015 in Lancashire that affected 300,000 homes.

What to do in case of a boil water notice?

Because viruses, protozoa and enteric bacteria present in liquids are sensitive to thermal inactivation, boiling tap water is an effective method for killing human pathogens. Different bacteria have different thermal inactivation sensitivities and inactivation times, but they become inactive at temperatures below 100°C. For example, E. Coli is inactivated at temperatures ranging from 60°C to 70°C when water is boiled for at least 300 seconds. Enteroviruses have similar heat sensitivity, however, the required boiling time at this temperature is 5 minutes.

Boil water notices will instruct people to heat water to a rolling boil, which is sufficient to inactivate pathogenic bacteria. Before consumption, water has to be allowed to cool naturally without adding ice, and during storage, it has to be protected against re-contamination. Also, when a boil water notice is issued, it usually means that unless you boil water as instructed, you should not use it for drinking, bathing, washing teeth, preparing and cooking food.

The boil water notice has to be observed until it’s lifted by the water company or local authority that issued it. While these notices are temporary, sometimes they can last for weeks, in which case water companies will distribute bottled water to households affected by the parasitic bug outbreak.

Shortcomings of boiling water

Boiling water does not remove certain contaminants (e.g. lead, sediments, chemical toxins), and it may even raise their concentration, therefore, more efficient methods to treat water at its point of use are needed. While not all water filters are efficient in dealing with pathogenic bacteria, multi-stage water filters like UV water filters equipped with pre and post filters and reverse osmosis systems will do a good job at not only removing pathogens, but also removing other types of contaminants that may be equally harmful for your health (e.g. chlorine, fluoride, heavy metals, pesticides, herbicides, VOCs, etc.).


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