A water pump is a manually operated pump that uses human power to lift the underground water to the surface.
A water pump consists of two valves V1 and V2. Valve V1 moves up and down along with the piston and valve V2 is connected to the base of the barrel. Similarly, the barrel is connected to a pipe and the pipe is inserted into the ground. When the handle is pushed down, the piston moves upward, which creates vacuum valves between V1 and V2. In this state, V1 closes, and water enters the barrel due to the atmospheric pressure. This process is called upstroke. When the handle is pulled upward, the distance between valves V1 and V2 decreases which cause an increase in pressure in valve V2 and gets closed. As a result, valve V1 opens due to water pressure and water flows out.