WHAT is the most precious commodity on earth? Well, it could be air, but water can also claim to be worthy of that top ranking.

Fortunately, the air and its vital oxygen are all around us, and no one has yet succeeded in taxing it or metering consumption.

Water is in a different category. There is plenty of it in and around Jersey for the taking, but most of it is salty and the natural fresh supplies in streams and ponds are full of potentially lethal microbes and contaminants. Jersey Water, a profitable company mainly owned by the Island public via the States, knows this and is good enough to pipe the stuff, suitably filtered and purified, into homes and businesses, charging only reasonable prices for this invaluable service.

However, although water is there to be had quite literally on tap, we still often choose to pay good money for cleverly marketed water in bottles. This may come from across the sea in France – where some varieties are said to have percolated through volcanic rock for millions of years but still carry a sell-by date – or from exotic locations all around the world. It is, for example, possible to obtain Fijian water, imported at massive cost from the tropical Pacific and regardless of the environmental cost of the ‘water miles’, the production processes involved or the ecological damage caused by billions of discarded plastic bottles.

Wherever it originates, water is water, so to pay pounds for the bottled article when the same thing from the tap costs mere pence looks like a kind of idiocy. Maybe so, but that does not stop restaurants and supermarkets from taking in the gullible and selling millions of gallons of H20 in fancy containers at fancy prices.

That factor is at the heart of the Environment Department’s new Time for Tap campaign, encouraging Islanders to favour the piped option. Its quality will be put to the test again this weekend at the Grassroots Festival, where the audience will be challenged to follow the example of States Members, whose meetings are now, so to speak, locally lubricated.

As the campaign’s titles suggests, the time has indeed come to say an emphatic ‘no’ to the bottled water fad and, in ninety per cent of circumstances in this part of the world, it is surely nothing more. At the risk of doing minor damage to the bottom line in the accounts of restaurants and retail outlets, we should all favour the clear, pure liquid that comes from the tap.

This is an easy matter at home – even if we insist on using high-tech filters to remove the faint tang of purifying chlorine – but faced by scornful wine waiters, we must all have the courage to say: ‘A carafe of your best tap water, please. And a few ice-cubes in too, if that is not too much trouble.’