DuraVent FasNSeal Eccentric Increaser: an offset step up that prevents condensate puddles
The DuraVent FasNSeal Eccentric Increaser is a stainless steel fitting that joins a smaller vent pipe to a larger one. Its larger end sits off center. On a horizontal run, that shape avoids leaving a low spot where condensate, the liquid dripping from the exhaust, can collect. DuraVent requires this fitting instead of a tapered increaser before a horizontal fixed blade damper, which limits exhaust flow. It goes on the damper’s side nearest the appliance. FasNSeal is DuraVent’s stainless steel vent for high efficiency gas boilers, furnaces, and water heaters, built to carry pressurized exhaust and its acidic condensate outside.
Choose the smaller and larger opening sizes on this page: 3 to 4 inch, 4 to 5 inch, 4 to 7 inch, 5 to 9 inch, or 7 to 9 inch. The fitting is stainless steel inside and out, with welded seams. An experienced venting professional handles the work, and DuraVent calls for a qualified inspector to check the whole run annually. Need the double wall version? See the DuraVent FasNSeal W2 Eccentric Increaser double wall fitting. The DuraVent FasNSeal Eccentric Increaser 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:








































