Collinear and coaxial venting are both “direct vent” solutions. Direct vent draws combustion air from the outside of the structure. Collinear uses two 4″ flex connectors. The first flex pipe runs to the top of the flue, the second flex pipe is installed into the damper area. Coaxial uses a 4″ flex connector inside of a 6″ flex connector. In most cases the collinear vent kit will work. However, with some smaller flues there is not enough room for two 4″ flex pipes and the coaxial kit will be a better choice.
Collinear and coaxial venting are both “direct vent” solutions. Direct vent draws combustion air from the outside of the structure. Collinear uses two 4″ flex connecters. The first flex pipe runs to the top of the flue, the second flex pipe is installed into the damper area. Coaxial uses a 4″ flex connector inside of a 6″ flex connector. In most cases the collinear vent kit will work. However, with some smaller flues there is not enough room for two 4″ flex pipes and the coaxial kit will be a better choice. Due to the problematic nature of top vent style units, the natural vent (B-Vent) kit should only be used as a last resort. For instance, if you have a large stone slab on top of the chimney that will not allow room for a direct vent cap.