Converting all UK hard water homes to soft water could save up to 8.24 million tonnes of carbon dioxide, equivalent to taking 1.8 million cars off the road or planting 136 million trees.

That’s according to new research by the manufacturer Harvey Water Softeners, which suggests energy usage with softened water is 23.8% lower for gas heaters and 17.8% for electric heaters, compared to hard water.

Hard water is water that contains higher mineral content.

Energy usage with hard water is believed to be higher mainly due to limescale build-up. Limescale is caused by calcium and magnesium being left behind when hard water evaporates.

It is estimated that around 13 million homes in the UK are in hard water regions and the average family of four living in these areas can accumulate 70 kilograms of limescale every year.

Limescale deposits within a heating system can cause blockages in pipework and boilers, reducing heating efficiency and increasing gas bills.