50 
BULLETIN 906, U. 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. 
