Our valve device, which is used to purge air from a plumbing system, includes a unitary, elastomeric body comprising top wall, a circumferential wall connected to the top wall, and a housing with a cavity that is accessed through a pair of ports. A closure element is moveably disposed within the cavity and responds to fluid entering one port to close the other port. An adjustable strap detachably wrapped around an exterior of the circumferential wall holds our device securely to an open end of a riser conduit of the plumbing system during testing for leaks. The circumferential wall has at least two wall sections of different diameters to accommodate different sized conduits.