Tap water in most developed countries is safe to drink, but that does not mean it tastes the same everywhere. Whether the source is lakes, rivers or underground aquifers, water providers remove physical contaminants and harmful chemicals, kill bugs and carry out frequent quality tests to ensure nothing has gone wrong. In less developed countries, where such infrastructure is often absent, travellers face real risks. Contaminated water can cause travellers’ diarrhoea or parasitic infections, so the advice is to avoid not only tap water but also ice in drinks and raw fruit and vegetables that may have been washed in it. Fruit is safe if washed in bottled water and peeled yourself, and bottled water should be used for brushing teeth. The UK Health Security Agency (UKHSA) has specifically warned about a surge of salmonella and shigella infections in Cape Verde that are suspected to have been caused by contaminated water, and now advises travellers there to strictly avoid the tap water. Those with weak immune systems may want to ask their doctor about taking antibiotics as a precaution. For more detailed regional guidance, the government’s National Travel Health Network and Centre provides information on high-risk areas including Mexico, Central and South America, most of Asia (excluding high-income countries such as Japan), most of Africa and most of the Middle East.
Why tap water tastes different
Travellers to Europe, North America and Australasia have much less to worry about on safety grounds, but many wince at their first taste of local tap water. The main reason, according to Professor Elena Berg, a biologist at the American University of Paris who also works as a water sommelier, is the level of dissolved minerals. “When the water rains down, it trickles through layers of rock and sand, and it picks up properties of those layers. Different minerals impart different flavour and qualities,” she explains. These minerals — calcium, magnesium, silicates and bicarbonates — are measured as total dissolved solids, or TDS. Typical tap water has a TDS of about 100 to 200 parts per million, while sea water is around 30,000. Water with a TDS that is too low can taste just as disconcerting as water where the TDS is higher than you are used to.
The contrast is easily seen between two British cities. Edinburgh’s tap water has a TDS below 50, while London’s can be as high as 350. The difference lies in the geology: water in the south and east of England runs through easily dissolvable limestone rocks, making it harder and richer in minerals, while the hard granite landscape of Scotland dissolves much less. Scottish tourism promoters claim Edinburgh water tastes cleaner as a result, but to a southerner it can taste oddly flat and bland. Similar variations occur across Europe. Water in the French Alps can have very high TDS values, giving it a faintly metallic taste. In Iceland, the hot water supply often has an “eggy” smell because the volcanic landscape dissolves hydrogen sulphide — although the cold drinking water is unaffected and the smell is harmless.
Other factors can also affect taste. If pipes bringing water to a hotel or home are rusty, metals such as iron, copper or zinc can leach in and produce a detectable metallic flavour; letting the tap run for a few minutes before using the water can help. Water treatment plants sometimes use a slightly higher dose of chlorine than you are used to, and while the residual taste or whiff is harmless, it can be off-putting. Professor Berg recommends filling a jug or large bottle with the water, leaving the top off and letting it rest in the fridge for half a day — the chlorine will evaporate, and the water will be chilled as a bonus. At tasting competitions, however, water is usually served at room temperature to enhance the flavour. Seasonal changes in temperature, runoff and algae growth can also influence mineral content and treatment adjustments, leading to variations throughout the year.
Bottled water: not necessarily better
Many people turn to bottled water when they dislike the taste of a local supply. Bottled mineral water comes from a single source such as a spring or aquifer, so it always has the same characteristic blend of minerals. A more recent trend, particularly in the United States, involves starting with ordinary municipal tap water, removing all the natural minerals and then adding back an artificial blend — a product usually called “mineralised” water. The companies claim it improves the taste, but there is no recognised health benefit to doing so.
Despite the perception that bottled water is superior, experts generally say tap water in countries like the UK is actually safer. The UK’s tap water undergoes so many checks for chemical and microbial contamination — more than a million tests every year — that the Drinking Water Inspectorate (DWI) has stated that “UK drinking water is amongst the highest in the world” in a Yale University ranking of national tap water safety. All common tourist destinations within Europe, such as France, Spain and Italy, score similarly well in the same ranking. Concerns about “forever chemicals” from plastics, such as PFAS, have been addressed by recent studies showing very low levels in drinking water in the first two UK regions studied; levels in water supplied in plastic bottles remain unclear.
Nonetheless, bottled water sales in the UK continue to rise by roughly 5 per cent a year, with no sign of slowing. About a fifth of UK households consume it rather than tap water. To reduce the environmental impact of plastic waste and carbon emissions from transport, Professor Berg advises buying bottled water from local sources rather than importing heavy water and heavy glass bottles. “We should really be appreciating our local water sources,” she said. For those put off by taste, filtering tap water at home with an activated carbon filter is an eco-friendly option that can remove chlorine taste and odour without the cost and waste of bottled water.