A water storage vessel (also known as a tank) that utilizes a gas burner to directly heat domestic water. Typical domestic uses of hot water are cooking, cleaning, bathing and space heating.
Another type of gas hot water heater is an indirect water heater. Designed to operate only with boilers, these gas hot water heaters use the hot water generated by a boiler to heat domestic hot water. Indirect water heaters typically provide at least 50% more hot water at lower operating costs than direct fired water heaters.