Water that has passed through the limestone under the Aldermere ridge picks up calcium and magnesium along the way. That is what leaves scale in your kettle and a film on the inside of a cup of tea. It is not a fault and it is not harmful.

Hardness varies across the catchment, from soft in the Thornbeck valley to hard around Ellerby Cross. Enter your postcode and we will show you the figure for your supply zone in the units your appliance manual asks for.

If you fit a water softener, keep one drinking-water tap unsoftened, usually the cold kitchen tap. Softened water is fine for washing but is not recommended for making up baby formula.