An isolation valve unit with a fusion outlet including a valve body comprised of a metal, such as brass, and having at least two ports, at least one of the ports including an overmolded thermoplastic end surrounding and enclosing the port from which the fusion outlet extends. In one embodiment, the thermoplastic end is composed of a PP-RCT material and is securely formed over the port by way of an over molding technique. The valve unit further includes a ball valve accommodated within the valve body and a handle for actuating the ball valve. The isolation valve unit is configured to couple to a larger polymeric pipe and to control the flow of fluids in a plumbing system via actuation of the ball valve.