Gas boilers with water tank

Gas with water heater

— a variety of gas boilers (see the relevant paragraph), supplemented by a water heater — a built-in tank for storing heated water. In addition to heating, such units were also originally designed for hot water supply. They are more convenient than conventional dual-circuit boilers (see "Type") because contain a fairly large amount (up to several hundred litres) of ready-to-use hot water. On the other hand, it takes some time to heat the water in the tank up.