A hot-water apparatus on the cylinder system, with secondary flow and return, to supply bath, lavatory, and two sinks, is shown by the accompanying figure. It will be noticed that the secondary return enters the cylinder about 4 in. to 5 in. from the top. The boiler should be boot-shaped in a 10-in. or 11-in. fire; 35-gal. cylinder; 1-in. branch to bath,?-in. to sinks, 4-in. to lavatory. Primary flow and return, 1 1/4 in.; secondary circulation, 1 in.; cold supply, lin.; expansion-pipe, 1 in. The emptying tap beneath the cylinder can be 1/2 in. or 3/4in. The stopcock in cold supply must have a full straight-way; this pipe must be a clear 1 in. everywhere. The size of the cold cistern depends on whether the water supply is constant or intermittent. In the latter case it will depend on the establishment, but 200 gal. to 300 gal. will be a likely size.

Cylinder System with Secondary Circulation.