DuraVent FasNSeal Tapered Increaser: a gradual step to a larger vent size
The DuraVent FasNSeal Tapered Increaser is a cone shaped stainless steel fitting that joins a smaller vent pipe to a larger one. Its gradual widening lets exhaust move through without the swirling caused by an abrupt size change. 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 a 3 to 4 inch or 4 to 5 inch transition on this page. For a horizontal damper, a part that controls vent flow, DuraVent requires an eccentric increaser instead.
The label’s arrow shows which way exhaust should travel. If a nearby straight pipe needs shortening, a professional can cut single wall FasNSeal at its narrow connection end, leaving at least 2 inches for the seal. The cut must be straight and any rough edges sanded smooth. DuraVent prefers using an adjustable length, and trimming a plain pipe does not make it adjustable. Need double wall venting? See the DuraVent FasNSeal W2 Tapered Increaser double wall fitting. The DuraVent FasNSeal Tapered 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:








































