What could be more natural or pure than water? We need to drink it for the sake of our health - 1.5 litres a day, according to EU recommendations. Water flushes waste matter and toxins through the body, promoting clear complexions. Drinking plenty of it helps weight loss. Moderate dehydration of the body can lead to migraine, headaches, dizziness and fatigue.

Marketing water to consumers, in this case, should be easy. The problem is, if there is little else as natural and pure as water, then there is also little else that is as readily available. We need to drink water, but do we really need to buy it? And if we do buy it, how do we decide what brand to choose?

"Bottled water is no longer seen as a luxury product, as perhaps it was in the 1980s," says a spokeswoman for Ballygowan. "It has become something that you would see people automatically putting in their shopping trolleys now. It is an everyday commodity."

Once upon a time, it would be pointed out that Evian, a leading French brand of mineral water, spelt "naive" backwards; people who bought in bottles what was available on tap in their own homes were gullible, it was suggested. The British Water Companies Association, which represents firms supplying tap water, described the bottled water market as one of the "great cons of the 20th century".

Yet the bottled water market in the Republic has grown by 120 per cent in five years, according to a recent report by Ballygowan, and is now valued at around £65 million (€82.5 million).

In 2000, the total volume sold increased by 30 per cent on the previous year, from 66 million litres to 86 million litres. This year, the expected total is approximately 95 million litres.

Bottled water, it seems, is shaking off the yuppie reputation it claimed in the 1980s, when attempts by the upmarket restaurant trade to sell sparkling mineral water at similar prices to soft or alcoholic drinks were met by sneers from dubious consumers.

Like all brands, leading Irish players Kerry Spring Water and Ballygowan try to sell not just simple grocery products but an image of a lifestyle to which consumers will hopefully aspire. The lifestyle attached to bottled water branding has shifted slightly from that of urban, affluent social groups to consumers who are active and health-conscious enough to opt for a "natural" choice.

"Bottled water is more convenient for people who are out walking or jogging. They can take the bottle with them," notes the spokeswoman for Ballygowan, which has a share of almost 50 per cent of the Irish market. The company's 750ml bottles with "push-pull" sports caps "will further consolidate Ballygowan's strong association with sport", according to the company's review of the Irish bottled water market.

Kerry Spring Water also emphasises its brand's association with active lifestyles, introducing lines such as H2 Sport. "People are looking for a healthy alternative to soft drinks," says Mr Declan Walsh, sales manager for Kerry Spring. "But whereas some products may have a label depicting people doing sports - but be nothing but water - H2 Sport has genuine isotonic properties and is competing more with energy products such as Lucozade," he says.

A recent report by consumer magazine Checkout Ireland lists Kerry Spring as the second-highest mover on its chart of Top 100 brands, up 16 places, thanks partly to its 40 per cent share of the flavoured water market. "Clear flavoured water did not exist five years ago but now it accounts for 14 to 15 per cent of the market," says Mr Walsh. Again, the health benefits are stressed: "It is a low calorie drink, with all the naturalness of mineral water," he adds.

The fashion accessory image does remain, however. Coca-Cola Bottlers relaunched its Deep River Rock brand last year with the advertising slogan "water you wear". Ballygowan has a number of what it calls "strategic brand-building sponsorships which reflect the brand's core values". These include sponsorship of RT╔'s fashion programme, Off the Rails.

Another Ballygowan sponsorship, the Ballygowan/ECO Young Environmentalists Awards, indicates how important it is for bottled water brands to project an environmentally friendly image. In May, a report by the World Wildlife Fund (WWF) criticised the industry for using 1.5 million tonnes of plastic every year to bottle water. Toxic chemicals, it said, could be released into the environment during the manufacture and disposal of the bottles.

In response, the Bottled Waters Association of Ireland pointed to legislation that requires Irish companies to pay about £50 for every tonne of plastic packaging they use in order to fund recycling programmes. "All bottles are recyclable and all labels bear the recyclable symbol," says the website for Tipperary Natural Mineral Water.

But the issue of plastic packaging is a genuine one, says Mr Walsh at Kerry Spring. "In Holland, Germany and Sweden, the industry has seen the emergence of Tetra Pak packaging as an offering for water, but it has been very, very slow to take off," he says.

"There has been a move from glass bottles to plastic in the market, and certainly it appears to be the acceptable norm for leading brands. We must also be aware of consumers' wishes and their happiness to purchase the product in this form of packaging." Portability, re-sealability and convenience are all key words.

But expansion in the bottled water sector may not simply be the result of its own branding and marketing strategies: the industry is the undoubted beneficiary of negative publicity for tap water.

In June, citizens' group Fluoride Free Water marched to the Department of Health, demanding that the Government stop fluoridation of water supplies. Pointing to links between fluoride in water to hip fractures, cancer and irritable bowel syndrome, members of the group carried placards reading "Poison on Tap" and bottles filled with thick, brown liquid collected from a kitchen tap fitted with a filter.

In August, householders in Grange, Co Waterford, started to buy large quantities of bottled water due to fears that tap water was contaminated with excessive nitrates. During the same month, Ballinasloe's Urban District Council advised people to use bottled water for drinking, teeth-brushing, salad-washing and making ice-cubes, following the discovery of e.coli bacteria in the town's main water supply.

But the WWF's report found that the marketing of bottled water brands as healthier than tap water was misleading.

Some bottled waters differed from tap water only in that they were distributed in bottles rather than through pipes, it said, even though there were more standards regulating tap water in Europe and the US than in the bottled water industry.