16 



BULLETIN 155, U. S. DEPARTMENT OF AGRICULTURE. 



The experience with 6-inch blow-offs on the Kings Hill pipes was 

 similar. Silt in the nipples became so compact that water could not 

 be forced through, and small holes were bored through the pipe to 

 drain it. Then the valves were removed and cleaned. Flushing 

 the valves occasionally would perhaps obviate this trouble. Where 

 the water carries extraordinary quantities of sand or silt it may be 

 advisable to provide sand boxes near the intakes. This was done 

 on the Santa Ana Canal in California, 1 the lower Yakima Irrigation 

 Co.'s canal in "Washington, and on other canals. 



On the 31-inch siphon at Prosser, Wash., a 12-inch valve was 

 used. (Sunnyside Canal, IT. S. Reclamation Service.) 



Where pipes are 



■5' 2" — H,, kept full during the 



winter, air valves and 

 blow-off gates should 

 be protected against 

 freezing. 



CONNECTIONS WITH OTHEE 

 KINDS OF PIPE. 



On the Sunnyside 

 Canal in Washington 

 the portions of the 

 Mabton and Prosser 

 siphons at intake and 

 outlet ends where the 

 pressures are light are 

 made of concrete pipe. 

 These are joined to 

 continuous stave wood 

 pipes which sustain 

 the greater pressures. 

 In other pipe lines wood is used for heads up to approximately 200 

 feet, and steel or cast iron for greater pressures. Again, where 

 curves too sharp for the wood pipe are required, in passing under 

 railroads and in other situations, it is frequently found necessary to 

 join continuous stave pipe to that of some other type. 



A common practice in joining wood and cast iron or steel is illus- 

 trated by Plate III, figure 2. The wood pipe is made to overlap the 

 metal pipe, and by means of the bands is cinched up to make a tight 

 joint. The usual lap is 12 to 18 inches, but laps of as much as 4 

 feet have been made. 



A connection of this kind is criticized on the ground that it does 

 not permit proper saturation of the wood pipe where it overlaps the 



Fig. 5. 



38w 



-Forty-eight-inch special tee for joining wood 

 pipe to east-iron pipe. 



1 Trans. Amer. Soc. Civ. Engin., 33 (1895), p. 129. 



