FARM WATER-WORKS 155 



rats which dig through the dams in winter and give rise to leaks 

 which, if undetected, may lead to the destruction of the dam. 

 Stone and cement facings or core walls will prevent this. 

 Usually there is little trouble from this cause where the inner face 

 is given a gentle slope. 



The method of piping will be essentially the same as described 

 in connection with gravity supplies from wells and springs. 



Gravity Supplies from Elevated Tanks. In the case of ele- 

 vated tanks, the distribution only is by gravity, some form of 

 pump being required to lift the water to the storage receptacle. 



Most of the tanks used in connection with farm water systems 

 have one or the other of three forms: (i) Wooden, (2) metal, 

 (3) cement. The wooden tanks are commonly of cypress with 

 adjustable bands of iron; the metal tanks are usually of galvan- 

 ized steel ; while the cement tanks are of the best quality hydraulic 

 cement with inclosed reinforcing irons. 



The location of a tank will depend principally upon the 

 material of which it is constructed and the amount of water to 

 be stored. A cement tank, because of the method of construc- 

 tion and weight, will have to be placed upon the ground, usually 

 upon the crest of a hill or similar elevation. A small wooden or 

 steel tank may be placed within the frame of a windmill tower, 

 or may be located in the upper story of a house or in the loft of a 

 barn. Larger wooden and steel tanks naturally require special' 

 towers, either of wood or steel. 



Cement tanks require considerable skill for their erection, 

 especially in the insertion of the reinforcing iron, and their con- 

 struction will seldom be desirable upon the farm. They arc 

 better adapted to the needs of small villages. 



In placing a tank in a house or barn, care must be taken to see 

 that the timbering is strong enough to support the load. The 

 weight of the water is easily calculated by multiplying the 

 capacity of the tank in gallons by 8 pounds. A 5OO-gallon tank, 

 which weighs, when filled, about 2 tons, is about as large as it is 

 safe to place within a house, although larger ones may be safely 



