Duravent DirectVent Stove Pipe 8-1/2" Pipe Extension

The 58DVA-08A pipe extension is used to fine-tune the total installed length of a DirectVent Pro vent run when the combination of standard rigid pipe sections — available in fixed lengths such as 6-inch, 12-inch, 24-inch, 36-inch, 48-inch, and 60-inch — cannot achieve the exact required total length without cutting. The extension's adjustable range of 3 to 7 inches provides a small increment that can bridge the gap between what the standard fixed-length sections provide and the precise total length required by the installation geometry. Common situations where the extension is needed include through-the-wall horizontal runs where the wall thickness and required pipe protrusion dimensions require a length that falls between two standard fixed-length sections, and vertical runs where the ceiling or attic height creates a similar mismatch.

The 58DVA-08A is a telescoping extension section — the overall body of the extension is 8-1/2 inches long but the inner and outer telescoping elements can slide relative to each other to shorten the effective installed length contribution to anywhere within the 3 to 7 inch range. The 3-inch minimum and 7-inch maximum represent the minimum and maximum positions to which the telescoping elements can be adjusted while maintaining the structural integrity of the connection. Once the extension is set to the required length position within that range, the twist-lock connection at each end is engaged against the adjacent rigid pipe section, locking the assembly in place. The 1-1/2 inch joint overlap deduction applies at each connection point in the same way as for all other DirectVent Pro components.

DirectVent Pro and DirectVent GS are two separate DuraVent coaxial direct vent systems that are not interchangeable, despite both being 5-inch by 8-inch nominal diameter. The two systems differ in their connection interface design — the twist-lock and component geometry of DirectVent Pro components are not dimensionally compatible with the connection interface of DirectVent GS components. Mixing components from the two systems creates joints that do not seal correctly, which can allow flue gases to leak from the inner exhaust pipe into the combustion air passage or into the building, or prevent the combustion air intake from functioning correctly. All components in a DirectVent Pro installation must be from the DirectVent Pro system family — if the existing system in a home is DirectVent GS, the correct extension for that system must be selected rather than the 58DVA-08A.

The 58DVA-08A and 58DVA-AB are the same DirectVent Pro 5-inch by 8-inch 8-1/2-inch adjustable pipe extension in construction, adjustable range, and performance — the only difference is the outer wall finish. The 58DVA-08A has a galvanized steel outer wall finish, while the 58DVA-AB has a black painted outer finish with laser-welded exterior seams. The black finish is typically selected for extension sections that are visible inside the living space — for example, in a vertical vent run rising above a gas stove through a finished room — where the black exterior coordinates better with the appliance and interior decor. The galvanized finish is equally functional and is the standard choice for sections that are not visible, such as those in wall cavities, attic spaces, or behind appliances.

The total installed length of a DirectVent Pro vent run is calculated by summing the nominal lengths of all pipe sections and extensions, then subtracting 1-1/2 inches for each joint connection in the run. For the 58DVA-08A, the contribution to the installed length is the adjusted telescoping position set during installation — between 3 and 7 inches — minus the 1-1/2 inch joint deduction at one connection end. For example, if the extension is set to its 7-inch maximum position, its installed length contribution after the joint deduction is approximately 5-1/2 inches. The total run length is then the sum of all pipe section installed lengths plus the extension installed length. Confirming the total against the appliance manufacturer's specified maximum and minimum vent run lengths is required before the installation is completed.

A complete DirectVent Pro 5-inch by 8-inch installation using the 58DVA-08A extension includes fixed-length rigid pipe sections in the 58DVA series for the main horizontal and vertical run lengths. Elbow sections — including the 58DVA-E90 90-degree elbow — provide direction changes. A wall thimble is required where the vent passes through a combustible wall. Ceiling support or firestop components are needed at ceiling penetrations. A wall termination cap or roof termination cap provides the exterior weather-tight termination. Wall straps support the vent run along wall surfaces. All components must remain within the DirectVent Pro 5-inch by 8-inch system family and must be confirmed as compatible with the specific appliance by the appliance manufacturer's installation instructions — the installation configuration, maximum horizontal run, and total system length limits are all governed by the appliance manufacturer's documentation.