Should I worry about drinking tap water?

Water, in case you are not up to date on the science, is good for you. It helps to regulate your body temperature, lubricates and cushions your joints, and aids your digestive system in getting rid of waste. Not drinking enough can affect your mood and disrupt your physical and cognitive performance, but getting plenty of it might help you safely lose weight, by aiding appetite regulation and increasing your metabolic rate. There is even some evidence that glugging enough might help you perform better in exams – though, of course, there might simply be a correlation between the sort of people who tote their own water jugs and those who study hard. H2O, in short, is great. But does it matter where you get it?

The short answer is: not really, if you live in the UK. “We have some of the best-quality tap water in the world,” says Peter Jarvis, professor of water science and technology at Cranfield University. “When you look at compliance against more than 40 water quality parameters – chemical and biological – we have more than 99.97% compliance to these standards in England and Wales, from more than 3.5m samples per year. The global Environmental Performance Index 2022, an annual Yale study which measures disease and death from exposure to unsafe sanitation and drinking water, puts us in the equal top six countries globally, with no reported diseases associated with our water infrastructure.”

So, if you are getting water from a tap, you are unlikely to imbibe anything nasty. But what about more recent concerns about contamination? “We need to keep vigilant – understanding what the emerging risks are and identifying ways that we can control those risks,” says Jarvis. “For example, our recent focus on this has been on investigating emerging contaminants such as the PFAS chemicals and microplastics, making sure that we maintain our treatment and supply systems to ensure they are resilient to the impacts of new challenges, climate change, and understanding the impact of environmental pollution on our water sources.”

With this in mind, is there a case to be made for drinking bottled water? Well, depending on who is doing the bottling, there are a few key differences. Tap water, for instance, will usually have a residual concentration of chlorine in it to ensure that it is safe as it is distributed across the country, and its composition will change depending on where you live. “Upland water sources tend to be softer, while lowland waters tend to have more alkalinity and hardness, which is why your kettle or boiler might scale,” says Jarvis. These soft and hard waters have a different taste – so if you are not a fan of the taste of tap, it’s worth considering investing in a jug filter.

Bottled water won’t contain residual chlorine, but – depending on where you get it – might be otherwise identical to tap water, as it is legal for businesses to sell water from public sources as long as the labelling isn’t misleading. Mineral and spring water, which sit in a different category, come from protected groundwaters that have been naturally filtered – removing most bacteria and micro-organisms – and have a very stable and consistent water quality, giving them a characteristic taste as a result of the mineral composition. “Each bottled water will have its own chemical composition,” says Jarvis. “And that will give it a distinct taste.”

As for whether those minerals are actually any good for you, the main ones you are likely to encounter are calcium and magnesium. If you struggle to get your recommended daily allowance, they will help to top you up, but if your diet is reasonably high in milk, cheese and green vegetables, you will already be getting plenty of the former, while spinach and avocado will take care of the latter. So there is a mild benefit to mineral water, but nothing you couldn’t get with a regime of tap and an otherwise balanced diet. In conclusion, then: get your water from the tap, filter it if you like, buy the fancy kind if you prefer the taste, and check the label if you suspect the supermarket is selling the standard stuff at a 2,000% markup. Just make sure you drink plenty of it: it’s the cheapest performance enhancer going.