241 such that the valve seal portion 240 is able to form a complete seal with the interior wall of the base 310 of the pump the one or more pockets 241 may provide additional space into which particulates may congregate as the valve seal portion 240 seals against the interior wall of the base 310 instead of being pinched between the valve seal portion 240 and the interior wall of the base 310 according to various embodiments of the invention an outlet valve 239 may include a valve seal portion 240 and one or more surfaces 242 extending away from the valve seal portion 240 towards the valve stem 233 such that when the outlet valve 239 is seated in or near a discharge passage 318 of a pump the outlet valve 239 creates a seal between the interior wall of a pump and the valve seal portion 240 one or more pockets 241 and a restricted space smaller than the one or more pockets 241 interior to the one or more pockets 241 as illustrated in fig2 a bellows 350 may be seated against a base 310 of the pump 300 a bellows 350 my include an inner rim ring 359 and an outer rim ring 357 straddling one or more base bellows rings 311 in the embodiment illustrated fig2 the inner rim ring 359 is not supported by a base rim 22 as with the configuration illustrated in.