5 type B gas vent 18 pipe length from the RV collection pipe lengths provide the core part of the chimney system. Pipes should match the inside diameter of all other pieces and all pieces should be from the same manufacturer. This round pipe is easy to assemble and can be combined to obtain the required installation height. There is a sectional overlap of 1.5, hence net assembled length is 1.5 less than listed length. The RV series offers round gas vent pipe and fittings for residential, commercial and industrial applications. It features a snap together, non-positional lock system, die formed ends and eliminates the need for all cutting, fitting and special engineering. It has an improved joint design provides for a rapid and secure connection in seconds. The use of our lock tab feature gives installers the option of engaging this tab instead of using sheet metal screws, when required by local code.