Placing the pump 20 meters up the hill would not work. The pump works by decreasing pressure (close to a vacuum) at the inlet, allowing normal atmospheric pressure (around 1013 millibars or 14.7 psi) to “push” the water up the pump's pipes. The theoretical maximum a sucking pump can reach is a vacuum, not more. The problem is that a water column 10.3 meters high will have enough weight to counter normal atmospheric pressure (which presses the water up from below), meaning that 10.3 meters is the maximum water can be “sucked” up.