A human-powered pump assembly includes a frame and a treadle pivot attached to the frame, such that the treadle pivot defines a horizontal rotational axis. The pump assembly includes a pair of treadles coupled to the treadle pivot and a rocker pivot attached to the frame, such that the rocker pivot defines a separate horizontal rotational axis. The pump assembly includes a reciprocating rocker coupled to the rocker pivot and to the pair of treadles to constrain the motion thereof, such that the rocker pivot axis is located below the treadle pivot axis.