For the water in the basin to follow one of the two paths, it is sufficient to close, by means of the proper cock, the pipe that places in communication the base of the pump body with the ascending pipe and leave the piston valve free to open.
In fact, in this case the water sucked into the pump body, since in the subsequent compression the valve at the bottom of the pump body closes and that of the piston opens, it passes above the piston which can be lowered completely.
Raising the piston once again, more water is sucked from the basin and again fills the pump body, while the water that was in it before goes into the glass above and, through the exhaust pipe, falls back into the basin, from which it can once again be drawn.
The process can be repeated and, in normal conditions, the same amount of water that is sucked up returns to the basin but, in the end, the pump body remains full. It is thus necessary to drain it through a narrow pipe with a cap placed before the cock in the pipe connecting the pump body and the ascending pipe.
For the sucked water to follow the second of the two paths, it is sufficient to keep the piston valve shut and leave open the cock that places in communication the base of the pump body and the ascending pipe.
In fact, during the subsequent compression, since the valve at the base of the pump body closes and the inlet valve in the ovoid tank of the ascending pipe opens, the sucked up water passes into the ovoid tank. ...continues