I'm pumping water with a mini pump through a plastic hose (1 meter), between two glass containers. My problem is that if I turn off the pump when the water is flowing through the entire hose, water keeps flowing at a lower rate till the water recipient is empty.
I'm thinking this is a pressure or inertia problem, but I don't know how to fix it.
One solution is adding an electric valve to the output but, if possible, I would like to avoid this. Is there any other thing I could do?
It sounds like you have a siphon, if your recipient container is positioned lower than the source container. Once water is flowing through the tube, it will continue to flow into the lower container with no pumping required, until the water level in both containers is at equal absolute heights. You start the pump, water starts flowing, but then keeps flowing even after the pump is turned off.
To eliminate the siphon effect, simply move your recipient container to a higher position than the source. Water will not flow into the higher container unless pumped. The water can temporarily flow through a higher position if the final destination is lower as seen with the siphon, but you can't spontaneously lift water from one container to a higher one without any energy input.
The reason your pump allows siphoning to occur is that it contains a pair of check valves inside it which prevent water from being pumped the wrong way while the motor is running. What this also means is that water can be drawn through the pump in the pumping direction even when the pump is turned off.
