A reinforced plastic valve apparatus in a preferred embodiment comprises an upper valve portion, a lower valve portion, an endoskeletal structure configured as a weir support or reinforcing member and an exoskeletal framework configured as a support collar. The upper valve portion preferably includes an upper plastic valve housing or body, a resilient diaphragm and a valve actuator. The lower valve portion comprises a lower plastic valve housing or body that is preferably configured to mate with the upper valve housing to define a valve interior. The lower valve body preferably has an integral weir which, in conjunction with the resilient diaphragm, defines a fluid passage. The diaphragm is configured to sealingly engage and disengage with the weir as effected by the valve actuator. The weir support member is disposable within the lower housing to support the weir.