This pump can still be found on farms everywhere. The maximum suction to the lower
valve (shown in red here; called the FOOT VALVE) is about 30 feet. Water enters
the lower chamber when the movable sealed plate is raised. The red valve is open
and the green valve on the plate is closed.
When the plate is pushed back
down, the red valve closes, and the liquid in the lower chamber is forced through
the green valve, which opens.
On the next upstroke of the plate, the liquid
which passed through the green valve on the previous downstroke is raised and
spills out the spout.
(This is a still
representation and possibly also a low-resolution image of a pump which is fully
animated in the CD-ROM version of this glossary.) 
