Water, water, everywhere. So why are we drinking it from plastic bottles?

In the last two decades Canadians have taken to bottled water like -- fish to water.

"I think it's cleaner and purer and I don't really particularly like the idea of drinking tap water," says one woman we talked to.

Canadians bought more than 700 million litres of bottled water last year. We spent about half a billion dollars on it. In a country with lots of fresh, free water, what we pay for it by the bottle is astonishing.

But water treatment systems do fail from time to time. News stories can drive people from the tap to the bottle.

Instead of turning away from the tap when there is the occasional problem, many people chose to drink bottled water all the time. And labels showing pure pristine environments further fuel the fad.

Many types of water

• spring water. Yes it comes from a spring. If it doesn't say spring, it isn't;
• mineral water, which is spring water containing minerals;
• and purified water.

Some is cleaned by adding ozone. Some is passed through high-tech filters. And a quarter of all bottled water comes originally from a municipal water source -- a tap.

We asked people why they choose bottled water over the stuff coming out of their taps.

"It's supposed to be better for you," says one woman. "It's supposed to be cleaner. Doesn't have as many chemicals in it."

We also asked if people notice any difference between bottled water and tap water:

"Not at all. No," says one man. Then why does his wife buy it? "I think it's a fad."

Then we asked if people would be surprised to find that scientists tell us that there is virtually no difference between tap water and bottled water and that tap water is totally drinkable.

"Actually no, I wouldn't be surprised," says one woman. "It's this mental block that I have that drinking water is better than tap water."

Pierre Payment says that "in most [of the] US and Canada water distributed as drinking water in the tap is very safe."

Payment is an internationally recognized microbiologist at the Universite du Quebec. He tested tap water in Quebec and found that a third of all gastrointestinal illnesses -- usually that means diarrhea -- are caused by the tap water. But such cases are rare, roughly translating into one mild illness every three years.

And that's not enough to make Payment switch to bottled water. But he has a more fundamental reason to drink tap water.

"I'm not an advocate for bottled water or water filtration devices," he says. "The main reason is a matter of cost for society… One cubic meter of water, of tap water, one thousand liters, costs about 50 cents, at the most, in most North American cities. Think about the cost of your bottled water at maybe... a dollar a bottle, it's extremely costly.

"What I'm saying is that the risk is so low that I prefer to tell my city authorities that I need better water, [I'm] willing to pay for it and put the rest of the money on something else which I like."

Elizabeth Griswold represents the biggest of the Canadian companies that sell water by the bottle.

"I think that it's up to the citizens of Canada to make that decision," she says, "and if they feel that they want to invest that type of money in the infrastructure of municipal water sources and have drinking water quality to wash their cars and flush their toilet, that's a huge expense for something that really is never consumed."

Does she think that bottled water is safer than tap water?

"When you compare bottled water to tap water, you're really comparing apples to oranges," she says. "And the reason why is because bottled water is regulated through the food and drugs act with Health Canada. And it is regulated just as any other food product is that you purchase in the grocery store. A lot of people don't understand that but it is a food product."

But aren't we simply comparing water with water?

"Well once you put it in a sealed container it is considered a food product in Canada and it has to meet the food and drugs act," says Griswold. "Municipal water supplies are not regulated by the federal government."

Many bottled water firms do claim their industry is more regulated than tap water. Scientists disagree, though.

"There's more regulation in fact for tap water," says Payment. "If you look at the number of the samples that have to be taken for the water that gets to your tap, it's huge. I mean, each distribution system has to be tested on a regular basis almost daily.

"There are regulations for chemicals. In fact, some people have been saying we would like to see bottled water to be regulated as much as tap water."

Payment says there are two reasons bottled water sells so well -- marketing and fear.

"The risk of chemicals in drinking water is low," he says. "Some people say it's a soup out there of chemicals. Well, if it's a soup, it's a consommé that's so diluted that there's almost nothing in it. So in that sense, chemophobia is part of the equation. The other is marketing."

And what marketing. Coke and Pepsi are now selling bottled water. So, on a positive note, it may be that bottled water is replacing less healthy sugar-laden pop.

But some bottled water marketing people will try anything. Consider their latest, oxygenated water. It comes in brands like Clearly Canadian O2, flo2 and OxEnergy.

The high oxygen in these bottled waters is supposed to be especially good for high performance athletes.

"The bulk of our water goes to the National Hockey League," says Tom Mohr, vice president of OxEnergy in Woodbridge, Ont. "We have teams like the Detroit Red Wings, the Toronto Maple Leafs, the Buffalo Sabres, the Dallas Stars; it goes on."

In fact, some of the players on the Dallas Stars, such as Mike Modano and Darryl Sydor, said OxEnergy gave them the boost they needed to win last year's Stanley Cup.

But scientists are skeptical. Duncan MacDougall is a kinesiologist at McMaster University in Hamilton, Ontario.

"That would have no effect on performance at all," he says. "In fact, if an athlete were counting on getting his oxygen through this medium, then he would have to drink several hundred litres of water during his hockey game."

So what does MacDougall thinks happened with the Dallas Stars?

"I've worked with a number of athletes and they can be a pretty gullible, gullible group and I suspect that nine out of ten athletes, if we gave them a product and said this is going to make you perform better, then nine out of ten of them would actually perform better," MacDougall says.

"So it's really the placebo effect or the suggestion effect of these products."

Tom Mohr says it's not just the pros who are winning with his oxygenated water.

"We have one gentleman that comes in who has a teenage daughter playing high school hockey," says Mohr. "And she suffers from asthma and has to use a puffer when she plays. And since she started drinking OxEnergy, she can play an entire game without using it at all. And we get a lot of those kinds of stories."

Consider another use for high-oxygen water, though, says MacDougall: "Pour them in your fish bowl and your fish will be able to exercise a lot better because of course, fish exchange oxygen directly from water, unlike humans."