If you’ve ever looked inside your kettle or boiler chances are you’ve probably spotted a tough, stony, off-white crust at the bottom of it. This is limescale, the deposit left behind by hard water.

The biggest problem, though, is that if hard water is heated past 55°C or left to stand, the dissolved minerals in it solidify as the moisture evaporates. These solidified minerals are what limescale is made of, and they can be a serious problem in the home. As you’ve probably noticed in your own home, limescale will often cover taps and hard surfaces with an unsightly layer that can be difficult to remove.

The visible effects, however, are nothing compared to those effects which can’t be seen. Hard water contains an average of 300mg of dissolved minerals per litre, so a four-person household can accumulate up to 70kg of limescale in a year. A significant amount of this stays inside central heating pipes, clogging them up.

Limescale also coats the heating elements of your boiler, shower, steam generator, washing machine, and dishwasher in the same way that it covers your kettle, thus making them less energy-efficient. In fact, British Water says that even a 1.6mm coating of limescale on a heating element can make it up to 12% less effective. This could cause you to waste up to £200 worth of energy every year. It could also cause your appliances to burn themselves out much more quickly than normal.