If water doesn't come out through the electric water pump, that is, if it dosen't take up water and it keeps running, air might enter it and it might stop working as well. What will be a natural way to describe that? I read "air entrainment", but I guess that it is rather formal. Is there any informal and natural way to describe that "air entering the pump"?
Turn it off, or air will enter into it.
Turn it off, or it'll take up air.