A discharge valve comprising a valve body, a valve member, and a valve seat. The valve body has a first end; a second end; a central axis therebetween; an inlet formed through the first end; a flow channel extending from the inlet to the second end; a valve channel extending from the inlet and terminating within the valve body; and at least one discharge port extending from the valve channel to an outer surface of the valve body. The valve member is substantially-spherical and movably disposed within the valve channel. The valve seat is disposed adjacent the first end of the valve channel. The valve seat has an orifice defined therethrough The valve member is movable between a first position, engaging the valve seat to substantially seal the orifice, and a second position adjacent the second end of the valve channel to permit fluid to flow through the orifice.