A valve is disclosed, the valve comprising a housing having an first opening and a second opening, and an elastomeric member positioned in the housing, the elastomeric member comprising a thickness, a continuous peripheral wall projecting from the thickness, and a slit extending through the thickness, a continuous portion of the peripheral wall creating a continuous seal- able contact with the housing and partitioning the housing into an upper section and a lower section, the elastomeric member configured such that upon creating a pressure differential between the upper section and the lower section of the housing causes either: (i) the peripheral wall to deflect from the housing permitting fluid flow around the elastomeric member； or (ii) the slit to open permitting fluid flow through the elastomeric member. Methods using the valve are also disclosed.
