see-through pump parts of pipepump econologica.org/pipepumps.html

[afripump]

interesting, see also the FairWater Afripump video on YouTube, also simple idea, and for water depths up to 100m. deep

[ut038]

Lifting of the lower flap valve turned out to be very hard to film. Is there if look very closely. Sequence is the same as standard pump. here the normal bottom check valve is replaced by the rubber flap valve which comes out with the shuttle for maintenance.

[ut038]

Technically call it a differential (positive) displacement pump. The net output 3/4 is the difference of the upstroke flow 1 and the downstroke flow (1/4). The retro loss substitutes for the down force normally required in the downstroke.