As altitude increases, atmospheric pressure decreases, thus exerting less "push" on the water entering the pumpsuction.
当海拔高度增加，大气压力减少，从而减少了作用于进入水泵的水的压力。
2
How it works: the piston moves from left to right, form a negative pressurepump cylinder, then the suction tank fluid through the valve into the pump cylinder.
工作原理：活塞自左向右移动时，泵缸内形成负压，则贮槽内液体经吸入阀进入泵缸内。
3
Pump up for suction then disconnect the bulb, pressure will stay.