FARM WATER-WORKS 153 



water from the well and a permanent circulation will be estab- 

 lished. 



Theoretically, water may be carried over a rise of more than 

 30 feet above its source, provided there is a still greater drop on 

 the other side. In practice, however, 20 to 25 feet is about as 

 high as it can be conveniently lifted. The chief difficulty arises 

 from the development of small leaks which admit air into the 

 pipe and destroy the vacuum. Also, more or less air is given up 

 by the water itself in its passage through the pipe. This collects 

 at the top of the bend and sooner or later the vacuum is destroyed. 

 If lead pipe is used and the lift is not more than 15 feet, the siphon- 

 age is seldom lost, but the farmer should never be without a pump 

 or other means of reestablishing the flow. If tight taps are pro- 

 vided at the discharge end, the flow may be shut off when not 

 needed and the waste of water thus prevented, but a leak may 

 admit air and destroy the vacuum. 



If the flow through a siphon is continuous, there will be com- 

 paratively little trouble from freezing and the pipe need not be 

 buried more than a foot or two. If it is to be shut off when not 

 in use, however, it should be placed at a depth of not less than 

 5 feet in the northern parts of the United States. Three feet is 

 commonly a sufficient depth in the central portions of the country, 

 and 2 feet or less for the southern portions. 



The cost of galvanized iron pipe at the factory commonly 

 ranges from about 3! cents a foot for f-inch pipe to 5^ cents for 

 f-inch, 7 1 cents for i-inch, and 12 cents for i^-inch. 



Gravity Supplies from Springs. - - To utilize the water of 

 springs an impounding reservoir will usually have to be con- 

 structed. This may consist simply in stoning up the spring to 

 hold back the surrounding earth, or it may require the construc- 

 tion of a small dam of earth or stone. In either case the labor is 

 usually slight, requiring only a few hours or a day or two at the 

 outside. A covering should also be provided to keep out aniiru 1 - 

 and leaves or other dirt. 



The service pipe should be placed far enough above the bottom 



