150 DOMESTIC WATER SUPPLIES FOR THE FARM 



depth in the summer when the water level is at b. The volume 

 at depth ac might be sufficient for the whole year, and that at 

 depth be insufficient to last through the summer. To preserve 

 the winter supply it is necessary to cement the bottom and walls 

 of the well nearly to the winter water level, as shown by the heavy 

 lines in the figure, thus converting it into a semicistern. When 

 this is done the well will fill during the winter to the level a and 

 will still contain water to about the level d after the ground water 

 has fallen to b. 



Combination wells and cisterns of this type are especially 

 dangerous if near any source of pollution, hence they are recom- 

 mended only for stock wells located at some distance from build- 

 ings and barnyards. They should be used for domestic supplies 

 only where on higher ground and at some distance from any 

 source of pollution. Cisterns completely cemented and covered 

 are safest where buildings are near. 



In some places it is the practice to turn the water from build- 

 ings into a well, but, although the well water is somewhat softened 

 thereby, there is no gain in amount, as water will not stand in an 

 ordinary well higher than in the outside ground, the equivalent 

 of the extra water turned into the well being lost by outward 

 percolation. 



House Tanks. - These are allied to cisterns but are constructed 

 of wood with water-tight linings and are located within the build- 

 ings instead of in the ground outside. Inasmuch as they are 

 filled by gravity it follows that they must be placed below the 

 level of the gutters. The most common location is in an L or 

 gable lower than the main building. 



Such house tanks have the marked advantage of affording 

 gravity supplies of flowing water on the lower floors. An auto- 

 matic cut-off may be installed in the leader outside, or the de- 

 flector may be so arranged that it may be worked from inside the 

 building. 



