The sketches below represent the two commonest schemes of hot-water apparatus in their simplest form. They would be erected tints for small property, and also for large property if some of the many special requirements or conditions to be found in large houses did not exist. Fig. 1 shows the cylinder system of apparatus, to which this name is given because in it a cylinder is nearly always used instead of the square tank. A square tank may be used when the apparatus only extends, say. 12ft. above it, but when more than this a cylinder is used, because a square reservoir will not bear the pressure. The connections must be made as shown. Draw-oils can be from any point on the expansion pipe up to the level of the water in the cold cistern. The reason the hot water does not run out of the top of the expansion pipe is that this pipe is carried up at least 2ft. higher than the cold-water cistern which feeds the apparatus. Fig. 2 shows the tank system of apparatus, so oiled because a square tank is used and not a cylinder, although the latter can be used if desired (the square tank costs less). In this apparatus the tank is fixed above the highest draw-off, and usually only a few feet below the cold-water cistern. The cold service is taken into the bottom of the tank, and an expansion pipe is taken from the top and carried to a height at least 2 ft. above the cold cistern. Draw-offs can only be taken from the flow pipe, not the return, as the latter seldom has hot water in it.

Forms of Hot-water Apparatus.