The laundry installed an innovative rainwater harvesting system, which allows the rain that lands on the hospital roof to be collected and used in the laundry. St John’s drains the water into storage tanks and then filters it for use in the laundry, which washes more than 10million items every year.

The scheme, which has reduced the hospital’s mains water usage by as much as 30%, was named Environmental Initiative of the Year at the awards ceremony, held at the Radisson SAS Hotel in Glasgow and presented in association with the Big Lottery Fund.

The awards recognised high achievement in a wide range of categories by individuals and teams from the public and voluntary sectors. NHS, Greater Glasgow and Clyde sponsored the environmental category.

Bill Mooney, the hospital’s estate manager, said the hospital had spoken to Scottish Water about ways to use “grey water” rather than just letting it drain away. He said the system cost £117,000 to set up, but had already paid for itself in reduced water bills.

Hospital bosses are currently considering a recycling system that will enable the laundry water to be reused.