It is often desirable to connect a boiler with two water-backs, one in the kitchen range and another in a laundry stove in the cellar for summer use. Fig. 15 shows the common method of making the connections. In this case either may be used separately, or both together without any adjustment of valves. The blow-off cock at the bottom of the lower water-back should be opened quite often to clear it of sediment, as it will collect much faster at this point than at the bottom of the boiler.

Fig. 15.