Limescale is a hard chalky deposit consisting mainly of calcium carbonate that often builds up wherever there is running water. While we are more used to limescale blocking the nozzles of our showers and tap, it has a very serious impact on your boiler’s efficiency. A limescale build-up of just one millimeter can increase fuel consumption by up to 2 percent. To prevent the buildup of limescale in your boiler, make sure you schedule regular maintenance with HVAC professionals.