Hot water is obtained by the installation of hot water tanks in the boiler room, inside of which tank a coil is placed, through which steam is passed, thereby heating the water in the tank; a thermostat should be placed on the tanks to control the water heating to the proper temperature. By the use of similar coils outside the tank, through which the water passes before it reaches the tank, the same results are obtained. The latter method, being a special device, is more expensive but more satisfactory than the former, as steam coils inside a tank gradually "pit" or wear, and leak, and are difficult to repair. Hot water is obtained also by the use of hot water heaters, which are small independent stoves which convey direct heat to water coils above them, and are run independently of the steam-boiler plant. A combination of the two methods of obtaining hot water is very satisfactory, as during the winter months the steam-boiler is used and furnishes the necessary hot water, without the added expense of running the additional small heater, whereas in the summer time, when the heating plant is shut down, the hot water heaters are used to obtain the necessary supply of hot water. In very large buildings, or where a high pressure plant is installed, and where power is furnished, steam can be used all the year for supplying hot water. It is important that the hot water tank should be sufficiently large to contain a surplus supply of water at all times, under even extraordinary demand. The problem of getting hot water varies according to the requirements of the particular building in which the plant is installed.