193. In this plan, Fig. 74, the same building and the same fixtures as those in Plans Nos. 2 and 3 are shown. The fixtures are all supplied from a house tank a on the top floor. This tank is filled with water from a rising main b which joins the service pipe c in the cellar. If the water in the main will not rise by its pressure in the service pipe to the tank, it must be forced. This can be done by attaching a lift and force pump either to b or c.

The system shown is well adapted to cases where the water supply is intermittent, such, for example, as in towns or cities where water pressure at best is low, and where factories, mills, and other works lessen the pressure during the day to such an extent that the water cannot run to the upper floors of the building.

If the water should rise high enough at night to flow into the tank, it may do so if the ball-cock k is open. The tank should be large enough to hold at least a 2-day supply.

Two cold-water distributing lines d, d1 supply cold water to the fixtures. The one to the left feeds the boiler. Stopcocks e and f, placed on these pipes just under the tank, shut the water off the building. Circulation pipes g, g1 run from the upper ends of the hot-water distributing pipes l,l1 to the boiler m, to insure a supply of hot water at the upper fixtures the moment the faucets are opened.

The hot-water pipes shown are made of iron or brass, and the cold-water pipes of lead, except those from the main, which are iron. The pipe h furnishes fresh water from the main for cooking and drinking purposes. Relief pipes i, i1, taken from the tops of the hot-water pipes, are turned over the top of the tank. To prevent a water hammer in c from affecting the ball-cock in the tank or in the meter n, a special air chamber is attached to the main at j. To secure a good flow of water throughout the building, the pipes may be of the sizes given, which are the nominal internal diameters.

In this system the boiler may be smaller than in Plan No. 3, or a larger waterback may be used, because considerable heat is transmitted from the hot water while it circulates through the building. A row of lever-handle stop-cocks is arranged over the boiler for convenience in shutting off the water.

The piping and connections in this plan are also exaggerated in size.