A housing assembly for a manifold includes a first housing with an inlet and a plurality of outlets, a second housing, and a valve retainer engaged with the first and second housings. The valve retainer includes a retention plate defined between first and second surfaces, a plurality of slot walls extending from the first surface, and a protruding edge that extends from a flanged lip and surrounds the plurality of slot walls. The retention plate defines a plurality of slots corresponding to the plurality of slot walls. The first housing may define a groove that receives the protruding edge, and the second housing may include a rim that engages the flanged lip of the valve retainer. Valve housings including first and second mating structures separated by wall segments may be positioned in outlets of the first housing and corresponding slots of the valve retainer.