9.9, 
BULLETIN 
U. 3. DEPAET3IEXT OF AGRICULTURE. 
lifted more than 100 feet, or where the working pressure on the pump 
does not exceed 65 pounds. 
Figure IS illustrates the application of this system to a farm home. 
PUMPING. 
The water level in shal- 
low wells is usually near 
enough to the surface to 
be within the limits of 
suction. The limiting 
practical suction lift for 
a pump is about 20 feet, 
although it will vary with 
the elevation above sea 
level. This means that 
the pump cylinder which 
raises the water by suction 
in lift pumps and which 
raises by suction and also 
forces the water in force 
pumps should not be more 
than 20 feet above the 
water level in the well. 
To practically eliminate 
suction lift the cylinder 
mav be submerged as 
shown in figure 19. thus 
making the cylinder and 
pump frame separate and 
connected only by a sec- 
tion of pipe. This pre- 
vents the valves from dry- 
ing out and makes the 
pump self-priming. Force 
pumps often have two 
cylinders, and in deep 
wells it is necessary that 
the lower or suction cyl- 
inder be either submerged 
or within at least 15 feet 
Fig. ".'.—Force pump with cylinder submerged in shallow-well. # ^i r lpx-il Tn 
the figure shown the forcing cylinder is within the suction cylinder. 
The suction of any type of pump must be air-tight. 
