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BULLETIN 906, TJ. S. DEPARTMENT OF AGRICULTURE. 



with valves as in the common orchard hydrant. The auxiliary pipe 

 acts as an overflow and is cemented to the outlet pipe, permitting the 

 excess of water to flow down the pipe line to the next hydrant. 

 A small spillway connects the two stands, the spillway being set 

 high enough to alio T a few inches head on the gates set in the 

 upper stand (fig. 10). A modification of this hydrant is fitted 

 with lift gates, so that all the water may flow down the pipe line 



and not be forced to 

 spill over the waste- 

 way of each valve. 

 Others have no 

 gates, all the water 

 being forced to rise 

 in each stand and 

 overflow into the 

 pipe line. Where 

 the valves are set on 

 a long lateral that 

 runs down on a 

 steep grade, it is 

 usually necessary to 

 provide gates in the 

 pipe line so water 

 can flow unob- 

 structed to any set 

 of valves. 



Another type of 

 overflow hydrant is 

 constructed by 

 placing a partition 

 wall in a single 

 length of pipe. The 

 water is forced over the partition wall when operating and spills 

 over into the outlet to the next valve. Small outlet gates that feed 

 the furrows are set in the inlet chamber, the presssure on the gates 

 depending upon the height of spillway above them. 



The third type is made of one large stand, consisting of one joint 

 of concrete pipe having a pipe of smaller diameter set inside. The 

 small pipe acts as the spillway and is connected to the outlet pipe. 



When these valves are constructed properly they are nearly ideal 

 for irrigating side-hill orchards, where only a small stream is re- 

 quired to each furrow. They are well adapted to contour and ter- 

 race plan of irrigation. 



Fig. 34. — Plain relief stand. Standpipe is high enough to 

 insure pressure on field hydrants above it. Excess pres- 

 sures on pipe line impossible, as standpipe will overflow 

 when all orchard valves above are closed. 



