A tubular base plate assembly has a lower surface connected to a heating system component and an upper surface. A tubular seal plate assembly is positioned above the base plate assembly upper surface having a mating surface facing the base plate assembly upper surface with a plurality of grooves therein. Sealing material is provided within the grooves. A tubular hub assembly is positioned above the seal plate assembly. A plurality of fasteners connects the seal plate assembly to the hub. A plurality of external brackets connects the seal plate assembly to the base plate assembly to secure the seal plate assembly. The sealing material forms a first gasket between the seal plate assembly and the base plate assembly.