HERE'S a wonderful modern sales technique. You go up to someone and say: "We'd like to sell you something you don't need because you already have it."

Now people like me who have an intelligent, rational attitude to spending money (my wife prefers the colloquial term "repulsive old miser") would respond: "No thanks. I already have the things I already have."

But the reply of the typical fanatical consumer (I prefer the technical term "my wife") is this: "Yeah! Sure! Bring it on. Here are the passwords to our bank accounts. Take what you need."

The best example of this is the bottled water debate.

For years, we had this amazing high-technology device in our home called "A Tap." Purified drinking water came out of it. We drank it. It was free. I never had to change the batteries. And the supply never ran out, even on days when the kids flooded the apartment with the stuff.

But now we have a Bottled Water Dispenser. Purified drinking water comes out of it. It costs a fortune. It uses electricity. It runs out constantly. Family members drink from it when they can and hang around parched when the delivery is late.

Now DO NOT TELL ANY MEMBER OF MY FAMILY this, but on the rare occasions I get home before they do, I fill up the water dispenser with ordinary tap water. Nobody notices.

A nutritionist told me that most bottled water is classified as "purified water" and so is tap water. "But there is a difference." she added. "Tap water supplies are checked for purity constantly and there’s an endless budget for keeping the system going. Bottled water supplies have rare visits from outside inspectors, sometimes once every few years."

After years of moaning to deaf ears about this, my pro-tap-water point of view is finally gaining ground.

At a water industry trade show

in Singapore a few days ago, specialists showed equipment they said could pipe the highest quality water to cities all over Asia. It coincided with a statement from the Earth Policy Institute that there was "a backlash against bottled water."

But the most powerful strand of my Tap Water Revival Plan concerns youth. You see, almost all young people these days are Global Warming Nazis. Taking a community's tap water, bottling it, driving it to supermarkets, and reselling it back to the community, is the single most wasteful activity on the planet.

The other day, one of my kids was sitting in the living room with all the lights on, plus the TV, plus the stereo, plus the computer, plus the iPod, plus the airconditioner, sipping chilled water from the cooler. I emerged from the kitchen, having popped in to drink a glass of tap water. She slipped off her headphones. "Dad." she moaned. "Turn the kitchen light off. You'll cause global warming and VAT'LL ALL DIE."

This type of passionate, irrational, youthful energy is the most powerful force on earth. When I marshal squads of youths all over the world to campaign on behalf of tap water as a cure for global warming, nothing will stop us.

My daughter and her friends will fearlessly stride into wine bars and point their fingers at shocked yuppies: "Put down that bottle of Evian. Or WE'LL ALL DIE." i And endless supply of wet humour can be found at wwa vittachi com