Inconsidering the general subject of country plumbing under a previous plate, allusion has been made to different methods of procuring a supply of water for use in the country, where there is no system of public supply. In addition to the attic-tank system, which is so generally used to supply country houses, there is another system, known as the pneumatic system of supply, which has many advantages over the old method. This system is of comparatively recent introduction, and depends in its operation upon compressed air. The use of this system is dependent only on the ability to procure a generous supply of water from a well, cistern, spring, or other source from which it may be pumped. A very important feature of this system is the fact that the tank may be located anywhere, either in the cellar, stable, underground, or at any other point where there is no danger of frost.
This allows a pressure to be maintained on the water piping, without the necessity of using an attic tank, with all its attendant evils, such as the danger of leakage, straining of timbers under its great weight, etc. The tank is of wrought iron or steel, air tight, and is generally filled by a power pump, pumping engine, or windmill pump, although, excepting as a matter of labor and convenience, it may be filled by the use of the hand pump.
Either a vertical or horizontal tank may be used, as most convenient.
There are several systems of pneumatic water supply on the market, the principal difference being in the methods employed in providing for the admission of air into the tank. In Plate 50, Fig. A represents the pneumatic tank located in the cellar, and Fig. B the tank located underground. The latter shows the use of a hand pump, and the former shows a lift-force pump operated by means of a brake. In both systems, which, by the way, are made by different manufacturers, it will be noted that both the force pipe from the pump and the supply pipe to fixtures, etc., connect into the bottom of the tank. A check valve between the pump and the tank is necessary, to hold the pressure in the tank when the pump is not in operation.
When the pump is in operation, a certain amount of air is pumped into the tank at every stroke, through a special form of automatic air valve. As the water rises in the tank, the air becomes more and more compressed, and when the tank has been filled about two-thirds full, it will be found that the air pressure is sufficient to force the water to any height ordinarily desired. In connection with the tank in Fig. A, a water gauge, seen at the left, serves to show the height of water in the tank, and a pressure gauge shows the pressure which the water is under, and indicates to the operator at the pump, when a sufficient pressure has been reached.
A pressure of 75 lbs. may be reached with the pneumatic system, and the manufacturers will guarantee a pressure of 50 lbs. The latter pressure is sufficient to raise water 100 ft., and as 20 lbs. or so is sufficient to raise it to the third floor or attic, it will be clear that 50 lbs. is ample for country use of almost any character. Manufacturers also guarantee to deliver water by means of this system through horizontal lines of pipe a mile in length.
The advantages of a pneumatic system are many. It not only does away with the attic tank, but allows the apparatus to be located conveniently to the pump, where it may be watched while the pump is running; the danger of freezing, common to elevated tanks placed out of doors, is avoided, also the expense of erecting towers to hold such a tank. An advantage to be gained in placing the tank underground, is that water delivered by it, is very nearly of a uniform temperature during all seasons of the year. The application of the pneumatic system of water supply covers a wide range, for it may be used in connection with a farm, for instance to provide a supply of water not only to the house, but also to the stables, carriage wash room, milk room, and may be used for lawn and garden purposes and in case of fire. The latter is a protection which country houses have always been sadly in need of, without the opportunity of filling the need. This same system has a much larger application in supplying institutions, factories, and even entire villages.
If the demand is not too great, one large tank may be used. Otherwise one pump working continuously, or during certain periods, can be used to fill as many tanks, located in different houses, as desired. For ordinary house use - that is, where the supply is to be used only for household purposes - a tank holding 400 or 500 gallons will be found satisfactory. Tanks for pneumatic supply purposes are generally tested under at least 150 lbs. pressure, and are therefore strong enough to produce any desired pressure.
The pressure produced in the use of the attic tank, however, is simply of an amount due to its height above the level at which water is delivered.
It may be stated that, in the use of a windmill pumping into a pneumatic tank, a regulating cylinder may be used, which will stop the action of the windmill whenever any given pressure in the tank is reached.