MMateoAug 16, 2026
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This page holds the DuraVent CVS concentric vent system, pipe and parts for pellet stoves, inserts and gas appliances whose makers approve the system. Exhaust leaves through the 3 inch inner pipe, while outside combustion air enters through the 5 inch outer pipe. Both paths share one opening through the wall or roof. Drawing outside air rather than heated room air helps reduce drafts.
Why use one concentric pipe instead of two?
You can use this line for pellet, corn and biofuel stoves and inserts. The inner pipe is stainless steel and the outer pipe is galvalume, with a painted black outer finish as the other choice. For gas appliances, the manual must approve this venting system and sets the run limits. PelletVent Pro carries exhaust only, while DirectVent Pro is the larger concentric line for direct vent gas fireplaces and stoves. Browse our pellet stove pipe collection if your manual calls for a PelletVent line.
What a CVS run is built from
Straight lengths come in 6, 12, 24 or 36 inches, all with one 3 inch inner diameter and the 5 inch outer pipe around it, so you pick a length and a finish, not a size. Align the dimples, push and twist to lock the outer pipe, with silicone rings sealing both pipes. Allow 1 1/4 inches lost at each joint. Fixed pipe cannot be cut, so use a telescoping length to fill a gap. Elbows handle bends, a tee provides cleanout access, and a pellet adapter joins the stove collar to the run.
Use a condensate drain only for condensing gas appliances, low in the run before the first elbow, never with pellet appliances. Match supports, wall thimbles, roof flashing and the termination to your route. The kit builder lets you choose a concentric vent kit for the run. For high-efficiency gas boilers, furnaces and water heaters, compare the FasNSeal and PolyPro vent lines against your appliance manual.
Why buy DuraVent CVS concentric vent from My Cozy Outdoors?
We are an authorized DuraVent dealer carrying the full DuraVent range. The full manufacturer warranty applies. Each of the maker's vent systems has its own parts, so do not treat lines as interchangeable. Send us the appliance model and a sketch of the run and we will write the parts list.
Concentric vent questions
What is a concentric vent?
It is one pipe inside another. Here, exhaust leaves through the 3 inch inner pipe, and outside air enters through the space inside the 5 inch outer pipe. Both share one opening, so combustion does not draw heated room air.
How does a concentric vent work?
The appliance sends exhaust through the sealed inner pipe and draws combustion air through the outer pipe from the same outdoor cap. Silicone rings seal the locking joints. Horizontal runs rise toward the wall cap, while roof terminations sit at least 12 inches above the roof.
Can you run a concentric vent through the roof?
Yes, you can route it through the roof. Use firestop supports at floors, an attic insulation shield, roof support, flashing, a storm collar and a vertical termination. Your appliance maker sets the allowed run length and number of elbows for DuraVent CVS.
