USE OF CONCRETE PIPE IN IRRIGATION. 
31 
open stands made of concrete pipe cemented together may be used 
for this purpose. The water will rise in the pipe connected to the 
inlet, and flow over a crest or notch into the other pipe, and thence 
into the main (figs. 8 and 9). The lateral pipe leading from this 
stand requires no gate, as the pressure will remain constant, allowing 
no excessive pressures to accumulate in the lateral. If a lateral slopes 
down grade from an overflow stand it is usual to provide a shut-off 
gate where the lateral branches off from the stand. The gate may 
be set in a low auxiliary stand that is cemented to the side of the 
main relief stand. 
Some relief stands 
consist of one large 
standpipe of suffi- 
cient diameter to 
allow an overflow 
pipe being placed in- 
side of it (fig. 10). 
Some orchard lat- 
erals have a 12-inch 
stand 6 to 18 feet 
high fitted with a 6- 
inch spillway pipe 
inside, the 6-inch 
pipe extending to a 
foot or so of the top 
of the 12-inch pipe. 
In this case water is 
diverted to the side 
lateral from the 12- 
inch pipe, the excess 
of water spilling 
down the 6-inch pipe 
into the main. There 
are a number of 
modifications of this principle that will be taken up in detail under 
the subject of diversion boxes and pipe structures. 
Nearly all measuring devices act as relief stands, especially weirs, 
miner's-inch boxes, and ordinary recording irrigation meters, as such 
devices are installed to allow the free flow of water over a crest in 
an open box. 
MEASURING DEVICES FOR PIPE IRRIGATION SYSTEMS. 
A number of devices are in use to measure the flow of water 
through pipes and laterals and from pumping plants and reservoirs. 
Of these the following are briefly discussed — Venturi meters, weirs, 
Fig 
-Overflow pipe in rear and small diversion box in 
front. 
