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DITCHING AND DEWATERING
5.60 THE WORK
FIGURE 5.50 Trash protection for inlet.
FIGURE 5.51 Mud protection for inlet.
Another inlet problem is that of the pipe and screen sinking into a muddy bottom and becoming
blocked, or being buried by soil washed over them. Placing the inlet in a wooden box will prevent
sinking and make it easier for the pump to suck up washings. See Fig. 5.51.
In long inlet lines, or large ones, it is good to have a foot valve in the bottom to hold water in
the pipe while the pump is not running, unless the pump is tight and the inlet is underwater at all
times. This will save time pumping out air each time the pump is started. Unfortunately, foot valves
are subject to jamming and sticking, and may need frequent attention to keep them working.
A whirlpool may form over the suction end of the inlet pipe, which will allow air to enter the pipe
through several feet of water. This is most apt to happen if the pipe is lying in a nearly horizontal
