[Illustration: FIG. 53.--Hand pump applied to air-tank.] _Pressure tanks._ A simple and very satisfactory method of storing water, and at the same time making provision for pumping water, is to place in the cellar or in a special excavation outside the cellar a pressure tank similar in shape to an ordinary horizontal boiler. The water in this tank is forced up into the house through the agency of compressed air, pumped in above the water, either by hand or by machinery, and in some cases automatically regulated so that the air pressure in the tank remains constant, no matter whether the tank contains much or little water. The village supply of Babylon, Long Island, is on this principle, the tanks there being eight feet in diameter and one hundred feet long,--much larger, of course, than is needed for a single house. [Illustration: FIG. 54.--Engine applied to air-tank.] The accompanying diagram and figures show the method of installing this system, which is known generally as the Kewanee system, although a number of other firms than the Kewanee Water Supply Co. are prepared to furnish the outfit necessary. [Illustration: FIG. 55.--Windmill connection with tank.] How the air-tank may be used in connection with a hand force pump is shown in Fig. 53. The water is pumped from a well into the tank, usually in the cellar, whence it flows by the pressure in the tank to all parts of the house. Figure 54 shows the tank with a gas engine and a power pump substituted for the hand pump. Figure 55 shows the using of a windmill in connection with the tank and also shows the relation of the tank to the fixtures in the rest of the house. CHAPTER IX _PLUMBING_ A generous supply of water for a house brings with it desires for the conveniences necessary to its enjoyment. As soon as running water is established in a house, the kitchen sink fails conspicuously to fulfill all requirements, and a wash-tub seems a sorry substitute for a modern bath-room. A single pipe supplying cold water only, no matter how pure the water or how satisfactory in the summer, does not afford the constant convenience which an unlimited supply of both cold and hot water offers, and the introduction of running water is usually followed by an addition to the kitchen stove whereby running hot water may be obtained as well as running cold water. The next step is the equipment of a bath-room, affording suitable bathing facilities and doing away with the out-of-door privy. _Installation of the plumbing._ These things are reckoned as luxuries, not among the necessities of life, and it must be understood at the outset that such conveniences cost money, both for original installation and for maintenance; the water-back in the stove will become filled up with lime if the water is hard, the boiler will become corroded and have to be replaced, the plumbing fixtures will certainly get out of repair and need attention, and there will be, year by year, a small but continuous outlay.