What's the best way to drink water?

The bottled water industry is booming, but it has a lot of people concerned, because unlike tap water, bottled water contains no added fluoride and fluoride is the magic ingredient which prevents tooth decay.

So we're posing the question: is bottled water rotting our kids' teeth?> Reporter Leila McKinnon will compare and contrast bottled, filtered and tap water.

Three volunteers in Sydney allowed us to collect samples of the water they drink at home.

First water sample:Tap water that had been drawn through a charcoal filter.

Second sample:Came out a kitchen tap, no filtering.

Third sample:Was retrieved from an office water cooler, the big bottle variety.

All samples were then analysed by a lab. All three different water types were tested for things like heavy metals (aluminium, copper and lead — these are some of the main impurities that bottled water and filtered waters are marketed as excluding), fluoride, and anything else that might be lurking in there.

Sydney tap water:Contained traces of lead and copper (from being transported in pipes) and fluoride, however the Australian Drinking Water Guidelines exist to assist in regulation of safe levels of heavy metals, chlorine and fluoride in tap water. Chlorine is added as a disinfectant, while fluoride is added to prevent dental decay across the community.

Charcoal filtered water:Contained no heavy metals, but had the same level of fluoride as tap water (which gets a big tick from the dentists).

Bottled spring water:Had no heavy metals present but a small level of fluoride was detected. This is a surprise as bottled water is supposed to be free of fluoride — but it's not. This particular sample contained about half as much fluoride as the tap water. By law (governed by the Food Standards Australia New Zealand) bottled water manufacturers are not allowed to add fluoride to their water. So why is there fluoride present in this sample of bottled spring water?

Tony Gentile, the Executive Director of the Australian Bottled Water Institute, is enlisted to clear up this mystery.

He explains that there are some small levels of fluoride naturally occurring in bottled spring water depending on where the water is sourced.

"It occurs naturally, bottled water is usually found in underground caves and the water is filtered through sandstone and you will find small amounts of fluoride occur naturally in almost all water in Australia," says Gentile.

Currently they are not allowed to add fluoride to bottled spring water, however, they would support the voluntary addition of fluoride, if companies wanted to market their product as having fluoride added. They do not support mandatory fluoridation of bottled water, as on the most part, the marketing edge for them is to provide an alternative purer water than that coming out of the tap.

So fluoride occurs naturally in water. But remember, our bottled water sample only had half as much fluoride as the Sydney tap water — and that's a problem according to the Australian Dental Association as within Australia, no additional fluoride can be placed into bottled water supplies. The majority of them don't provide fluoride at a level where it's going to produce a known benefit.

The key benefit of fluoride is that it hardens tooth enamel, making our teeth resistant to the acid that causes decay.

Dr Robert McCray, a dentist as well as the Qld President of the Australian Dental Association, says that all those who prefer bottled water have no idea what they're missing out on.

"If you are living in a community with a fluoridated water supply, and your consumption of drinking water supplies comes mainly from a bottled source, then your experience of dental decay has a strong likelihood to increase," says Dr McCray.

So should parents be concerned there isn't fluoride in bottled water for their children's teeth?

No according to Gentile. "The most important thing about dental health is dental hygiene. Bottled water is consumed by very few people usually at the higher earning families. These families usually have very good dental hygiene," he says.

So what's the best water to drink?

Tap water contains heavy metals and fluoride, however, Australian water quality guidelines exist to regulate safe consumption levels. The charcoal filtered tap water eliminates heavy metals and retains the same level of fluoride as already existing in the tap water, while bottled spring water is free from heavy metals and it may contain fluoride naturally. Arguments both for and against water fluoridation exist, some saying it is essential for dental health, others claiming negative health affects deriving from fluoride.

When it comes to healthy teeth, everyone agrees that choosing to drink water, whether bottled, filtered or tap, is a wise choice!

There's one more thing you should know: even if you're a fan of tap water, it doesn't always mean you're getting the fluoride you need for your teeth.

• Bottled water manufacturers are not obliged by law to say on their labels whether or not the water contains fluoride. So unless you ring up the company yourself, you'll never know!
• Sales of bottled water are growing by about 10 percent a year, not surprising considering families are stocking up at home and we generally drink out of water coolers at work.
• Is it safe to drink from the garden hose? No. For a start, chemicals from plastic hoses can leech into the water. Second, the thread at the end of the hose can be contaminated with germs. Third, non-drinking water can get sucked back into your hose after you've cleaned the pool, or filled a bucket, or cleaned a drain. The bottom line? It's not a good idea!