I ordered a new petcock for my XT350 tank install. The petcock came with the gasket for the top surface that contacts the tank, but no gaskets for the screws (which were not included with the petcock). I got a set of screws along with some other used XT350 tank parts separately. Are the washers on the screws and the gasket on the petcock sufficient to keep it from leaking or does it need additional gaskets or sealant/teflon tape for screw threads? Parts diagrams just show the washers and nothing else - anyone know?