DuraVent FasNSeal W2 Double Wall Increaser Wye: joins a smaller boiler branch to a larger shared vent
The DuraVent FasNSeal W2 Double Wall Increaser Wye is a stainless steel fitting that joins a smaller branch to a larger vent run. Its branch enters at a 45 degree angle, combining the junction and size change in one piece. It lets a smaller boiler outlet feed a larger shared exhaust pipe, but only when the appliance maker approves connecting boilers this way. The branch can be up to 6 inches smaller than the main run. FasNSeal W2 is DuraVent’s double wall stainless steel vent for high efficiency gas boilers, furnaces, and water heaters, with an air space between its two walls.
Choose the branch and main run sizes together on this page, with combinations from 6 by 10 inch to 12 by 14 inch. An experienced professional fits the entire run using FasNSeal parts. If the route passes through a wall, the W2 wall thimble, a sleeve around the vent, needs an opening 6 inches larger than the vent size. That sleeve is optional through a wall made of materials that cannot burn. Need the single wall fitting? See the DuraVent FasNSeal Single Wall Increaser Wye. The DuraVent FasNSeal W2 Double Wall Increaser Wye ships free from My Cozy Outdoors with No Sales Tax (except WY) and the full manufacturer warranty.












Commercial projects may require custom parts and unique system designs. Duravent offers complete project assistance:








































