It has been described as the ultimate marketing trick, but the allure of bottled water is something more and more people are swallowing. With global sales set to overtake those of soda, The Food Chain asks why so many of us are paying for something we could easily get for free.

With prices of some bottles hundreds of times more expensive than the tap we visit a water testing lab to see if there is any difference between them.

The industry claims it offers a healthier alternative to soda drinks, but opponents say it causes unnecessary environmental damage. We find out how bottled water is coming under attack in drought-stricken California, and whether the criticisms are fair.

In parts of the world where safe drinking water is difficult or impossible to come by, can bottled water be a lifesaver? We have a report from Tanzania's capital, Dar es Salaam.

Plus, we speak to Marco Settembri, head of Nestle Waters, one of the world's biggest water bottling firms.

(Photo: A man stores bottles at a warehouse in Afghanistan. Credit: Noorullah Shirzada, Getty Images)