WATER SUPPLY FOR COUNTRY HOME 



481 



pressure; therefore there are about 45 cu. in. of air in solu- 

 tion to each cubic foot of water as it enters the tank. The 

 water in the tank is kept constantly under a pressure of, at 

 least, 2 atmospheres; the water, therefore, as it escapes from 

 the tank through the pipes and faucets, contains at least twice 

 as much air as it did in the well. Evidently, if no additional 

 air were pumped into the tank, the tank would soon become 

 "water-logged." What would be the result? 



563. Shallow Well Water Often Dangerous. We have seen 

 that wells are supplied by the ground-water. It is evident 



FIG. 294. Why shallow wells are dangerous. 



that, if the walls of the well are merely bricked up to prevent 

 the walls from caving in, they will not be water-tight. In 

 such cases surface water, at times of frequent and heavy rains, 

 will readily enter the well very near its top. If such a well be 

 located near a barnyard on a farm or in a somewhat thickly 

 settled portion of a town or city, especially one not provided 

 with sanitary sewers, the surface soil about the well will be 

 contaminated with manure and other decaying animal and 

 vegetable matter. The surface waters, at times of heavy rains, 

 may enter at the surface or, at best, merely soak a few feet into 

 the soil before finding its way into the well (Fig. 294, also the 

 Frontispiece). 



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