Cornwall County Council has said it spent more than £44,000 on bottled water in a year.
The council said it was moving away from using bottled water
A survey of Welsh and English councils for the BBC's Panorama programme put it 37th out of 383 councils on an expenditure list.
The council said it was replacing bottled water with systems which used filtered mains water.
The programme found councils had a £5m-plus bottled water bill. Penwith Council, Cornwall, spent nothing on it.
The county council spent £44,296 on bottled water between October 2006 and October 2007.
It said that the 2006/7 figures were a £31,154 decrease from the year before, when it had spent £75,450 on water during the 2005/6 financial year.
The council added that had replaced virtually all bottled water fountains in New County Hall with a system which uses filtered mains water.
It said it was now committed to introducing a similar system in all its other establishments where possible.
The Panorama programme, to be broadcast on BBC One on Monday, investigates the monetary and environmental costs of bottled water consumption in the UK.
The programme made a Freedom of Information request to many of the councils in England and Wales to find out how much they had spent on bottled water in the previous financial year.
The total figure came to more than £5m, with Hampshire topping the table. It spent £141,215 on bottled water between November 2006 and October 2007.
UK Environment Minister Phil Woolas has described the amount the country spends on bottled water as "morally unacceptable" and is urging people to use tapped water instead.
Panorama: Bottled Water - Who Needs It? will be shown on BBC One at 2030 GMT on Monday