DuraVent Type B Gas Vent Diameter Increaser - 3" to 4" Length: A venting pipe with a 3" inner diameter is required for this unit. It is sometimes necessary to extend the diameter of a gas appliance vent during installation. When using DuraVent Type B plumbing, you should always maintain some Gas Vent Diameter Increasers on hand. DuraVent's Type B Gas Vent system is for use with natural gas or liquid propane category I and draft hood equipped appliances and appliances tested and listed to use Type B Gas Vent for a wide range of applications including: natural gas fireplaces, gas fired furnaces, boilers, water heaters, and wall or space heating applications. Round Type B Gas Vent 3" - 8" and oval 4" - 6": Made of aluminum .012" inner wall galvanized .018" outer wall. Round Type B Gas Vent 10" - 16": Made of aluminum .016" inner wall galvanized .021" outer wall. Round Type B Gas Vent 18" - 30": Made of aluminum .020" inner wall galvanized .021" outer wall. 3"-16" diameters have the twist-lock fittings screws that you need for 18" and larger diameters. You should have a 1"clearance to combustibles in single and multi-family dwellings. Listings - UL Listed to UL 441 and UL 1777 (MH6357). ULC Listed to ULC S605 (CMH1276 & CMH1407).

Increases vent diameter For use with Dura-Vent Type B Gas Vent pipes 4" tall 25-year warranty