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Planning the Venting System


Location of the termination of the venting system should comply with the National Fuel Gas Code, A.N.S.I. Z223.1, manufacturer's recommendations and/or applicable local codes.

A. The exit termination of a mechanical draft system must not be less than 7' above grade when located adjacent to the public walkway.

B. The vent termination of a direct vent or sealed combustion appliance with an input of 50,000 BTUs per hour or less must be located at least 9" from any opening through which vented gases could enter the building. With an input over 50,000 BTU's per hour, a 1' termination clearance is required. Another term for direct vent is sealed combustion.

C. The venting systems, with the exception of direct vent appliances, must terminate at least 4' below, 4' horizontally, or 1' above any door, window or gravity air inlet into the building.

D. The bottom of the vent terminal must be located at least 1' above finished grade.

E. A venting system must terminate at least 3' above any forced air inlet located within 10'.

F. The vent termination point must not be installed closer than 3' from an inside corner of an L-shaped structure.

G. The vent termination should not be mounted directly above or within 3' horizontally from an oil tank vent or gas meter.

Clearance to Combustible Materials

Single Pipe System  
Allowable Inlet Temperature 
Clearance (B) 
400° F or less 12" min. 
550° F or less  12" min. 


Insulated Double Pipe System  
Allowable Inlet Temperature 
Clearance (A) 
400° F or less  2.5" min. 
550° F or less  2.5" min.

If mounting the venting system near combustible materials, refer to the diagrams above for allowable installation clearances. Clearances are based on an installation using single wall steel vent pipe. If manufactured, double wall vent pipe is required or used for the installation, clearance should be based on the vent pipe's rated clearance. Always check local code requirements for code restrictions.

Routing of the vent system and clearances for the vent pipe may be planned once the termination location is determined. Route the vent pipe from the stove to the venter using as few elbows as possible. The horizontal section of the vent pipe should have a slight upward slope from the stove to the venter. The vent pipe size (diameter) can be smaller than a typical chimney vented system and still overcome the higher pressure losses because the power venter mechanically creates the required draft or airflow to vent the system.