A rotary, self-priming, positive displacement pump is described. The pump may include a pump housing including an inlet and an outlet, a pump chamber including an upper wall, a lateral wall, and a floor, first and second rotary impellers in the pump chamber, and a pair of gears each secured to the first and second rotary impellers, and a pressure relief feature operable to relieve pressure developing in a relatively high pressure zone of the pump chamber. The gears mesh with each other to ensure that the vanes do not contact one another during rotation. The pressure relief feature may comprise one or more channels formed in the pump housing and/or the first and second rotary impellers. The channels connect the high pressure zone with another zone to redistribute pressure. The channels may include one continuous channel or alternatively, a plurality of unconnected channels.