Tap water vending machines could be installed in Tube and rail stations across London.
They would allow commuters to refill their water bottles, either for free or for a small charge, under plans announced by Thames Water today.
Andrea Riding, community liaison executive for the company, said: "There is a real momentum behind tap water but for people on the go it is a real problem. These machines would allow every rail and Tube station to offer free, chilled tap water.
"I think we have seen a real sea change in the attitude of Londoners to bottled water and now we hope we can bring that choice to people on the move as well."
She said Thames Water was in negotiations with several large agencies, includingTransport for London, about the scheme.
Mrs Riding continued: "We would hope that a company like TfL would run the operation and we think the machines would be a welcome addition to every Tube and bus station.
"It's something that will appeal to everyone, as you can simply fill a bottle on your way to work, then again on your way home."
The vending machines require a power socket and a connection to the water mains. They filter and chill the water and are also capable of selling reusable water bottles. Mrs Riding said the company was hopeful of winning the support of Boris Johnson, adding: "We worked with Ken Livingstone on this idea, so we are hopeful the new mayor will back it as well.
"There would be a nominal charge of perhaps 20p per half litre to cover the cost and upkeep of the machine but we are hopeful that a major sponsor could be attracted.
"The sponsor could have their advert on the machines and bottles and that way it should be possible to offer free tap water to everyone."
The announcement of the project comes in the wake of the Evening Standard's Water On Tap campaign, which aims to reduce the amount of bottled water Londoners consume because it is environmentally unfriendly.
More than 3,000 restaurants, bars and clubs in London have signed up by pledging to offer their customers free tap water alongside bottled.
The public's perception of bottled water is also changing. Shop sales fell by nine per cent to £284million in the year to March, according to independent retail analysts TNS