Abstract: A boiler in which water is heated by passing through a furnace has a plurality of pipes for carrying water through the furnace. Each pipe is formed from high-carbon steel and is provided with a non-magnetic, electrically conductive inner lining. The lining, which is preferably electrically grounded, may be formed for example from copper metal, copper-filled organosilicon or copper-filled fluoroplastic material. In an alternative, or supplementary, implementation of the invention, the water circulation system of the boiler is provided with a plurality of magnetized granules. The granules, which preferably have a density of between about 0.5.times.10.sup.3 and about 1.0.times.10.sup.3 kg m.sup.-3, are carried through the boiler pipes by the water flow and help to reduce corrosion and scale deposition within the pipes.