And yet we buy bottled water anyway, in enormous quantities. Each person in Britain now drinks an average of 33 litres per year, and consumption has doubled in the past five years, according to the latest figures from market researcher Mintel. This year, we will spend £1.7bn on around 2bn litres of the stuff. Globally, bottled water is now a £25bn industry, and its consumption is growing faster than that of any other drink. Why has it become so popular?
It cannot be the taste, given that most people cannot tell the difference. Indeed, much bottled water is derived from municipal water supplies, though it is sometimes filtered, or has additional minerals added to it. Its greater "purity" is an illusion. In one study, published in the Archives of Family Medicine, researchers found that a quarter of the samples of bottled water tested had significantly higher levels of bacteria than tap water in Cleveland. The scientists concluded that "use of bottled water on the assumption of purity can be misguided". Nor is there any health or nutritional benefit. Another study by the University of Geneva found that bottled water was no better from a nutritional point of view than tap water.
Fashion and convenience have much to do with water's popularity: the practice of carrying a small water bottle around was pioneered by supermodels, and a bottle of water is more portable when you are out and about on a hot day. But why not refill the bottle in your bag from the tap?
Of course, that is not an option for many people in the developing world. And that is why I find the enthusiasm for bottled water not simply illogical or peculiar, but distasteful. For those of us in the developed world, safe water is abundant, yet we decadently choose to shun the tap water under our noses, and drink bottled water instead. Our choice of water has become a lifestyle option. For many people in developing countries, however, access to water remains a matter of life or death.
More than 2.6 billion people, more than 40% of the world's population, lack basic sanitation, and more than 1 billion people lack reliable access to safe drinking water. The World Health Organisation estimates that 80% of all illness in the world is due to waterborne diseases, which kill around 5 million people a year.
Meeting the UN's goal of reducing by half the number of people without access to clean water and sanitation by 2015 would cost £6.2bn a year beyond current spending on water projects, says the International Water Management Institute. This is less than a quarter of global annual spending on bottled water. I have no objections to people drinking bottled water in the developing world; it is often the only safe supply. But for those of us in the developed world, it is time for a rethink.
How about a tax on bottled water, with the proceeds being used to fund water projects? The problem is that it is very difficult to ring-fence tax revenues in this way, and it would then be up to governments to decide which water projects to support. What about "ethical" water, such as the new Ethos Water just launched by Starbucks, where a small donation from every bottle sold goes to water charities? I applaud the sentiment, but the donation is tiny, and it does not address the heavy environmental costs associated with bottled water, which is shipped at vast expense from one part of the world to another, is then kept refrigerated before sale, and causes huge numbers of plastic bottles to go into landfill.
I have concluded that the logical response is to stop spending money on bottled water altogether, and to give the money directly to water charities, such as Water Aid, instead. If you can, try filtering the water, either using a jug-based or tap-based filter. It will soon pay for itself, given that bottled water costs between 250 and 10,000 times as much as tap water. So give your tap water another try. You may conclude, as I have, that bottled water has an unacceptably bitter taste.
· Tom Standage is technology editor of the Economist and the author of A History of the World in Six Glasses (Walker & Company).