Paying for water - like tipping and bread - is one of those vexed restaurant issues most likely to divide a room. And now that the water for sale isn't just about the fancy bottled stuff (increasingly coming via kegs or filtration systems) and is being sold in numerous ways (per bottle, head, carafe) it seems that there are a host of new ways for it to continue ruffling feathers.

The resentment some feel when asked if they'd like "still or sparkling" may come from the age-old perception that restaurants are out to gleefully price gouge them, or to sneer at them if they opt for the humble tap. And while those perceptions are generally wide of the mark, some restaurateurs admit to excellent profit margins from selling water and, therefore, from encouraging people to ante up.

Adam Cash, co-owner of Richmond's Union Dining, says that "selling bottled water can be a real revenue stream for restaurants, particularly if you find an Italian company that will sell you a bottle of water for under $1 and you're charging $10 a litre".

Even so, Union Dining, after a brief stint selling Victorian bottled water, now peddles its water via a leased Australian system called Vestal that filters tap water using an osmosis filter to remove chlorine and fluoride. Carbonated or still, it costs $7 for 750 millilitres.

"I went to the States a few years ago and a lot of the great restaurants there had in-house water systems that cut down on food miles and packaging and I liked that," says Cash. "We don't make much money out of it, but for those, like me, who love drinking sparkling water with their food, it's a good, guilt-free option."

Mark Best, co-owner and chef at the city's Pei Modern and Sydney's Marque restaurant, has had Italian filtration and carbonation systems installed in both his restaurants and charges $5 for as much water - still or sparkling, chilled or ambient - as people can consume.

"They can have gallons if they want," he says. "And they do. We had a bit of flak to start with but mostly people understood what we were doing in terms of cutting down on glass and refrigeration and so on. I'll put my hand up and say I've made a lot of money over the years with mineral water and I've probably taken a cut in profit now but this way just seemed to make so much more sense."

Not every restaurateur is comfortable charging for water. At Albert Street Food & Wine, in Brunswick, co-owner Ruth Giffney is dubious about filtration.

"What you're basically doing with those is selling carbonated tap water," she says. "And that's not something I felt that we could do ethically, especially in Brunswick."

The sparkling water on tap at Albert Street Food & Wine is naturally carbonated mineral water that comes in a reusable keg from Daylesford & Hepburn Springs Co and costs $8 a litre.

"What we offer here is basically a choice of chilled sparkling mineral water or tap water at room temperature," says Giffney. "It's about sustainability but also I don't see the point of selling still water because we live in Melbourne and the tap water here is very good. To be honest, I've never been asked for bottled still water and I've never worked in a place where I've filled up so many jugs of tap water."

The fetish for exotic bottled waters from far-flung places (South Africa's Blue Republic came from "the cradle of mankind") - it reached its peak five years ago and brought the unwelcome terms ''water menu'' and ''water sommelier'' with it - seems to have mostly run dry. These days, even top-end restaurants such as The Press Club stick with the San Pellegrino-like stalwarts, selling it at $6 for as much as you can drink.

It's the sort of approach that can make paying for water appear less like a luxury and more like a regular part of the meal. Still, "tap" remains a perfectly acceptable request.