Vent termination heights and sealing

What is going on

Heights and sealing for vent and combustion air terminations. Applies to roof and wall. Snow burial and poor seals are the usual faults.

Likely causes

• Termination below snow level
• Unsealed roof or wall penetration
• Coupling and pipe length wrong in wall
• Pipes in different pressure zones

Check in this order

1. Terminate at least 12 in above the highest anticipated snow level.
2. Keep the horizontal termination at least 12 in from grade or snow level.
3. Seal a roof penetration tight with proper flashing, like a plastic plumbing vent flashing.
4. For a horizontal wall penetration, install a coupling on each side of the wall and solvent cement a pipe between them. Pipe length equals wall thickness plus socket depth of both fittings.
5. Seal the wall penetration with silicone caulk.
6. Terminate both pipes in the same pressure zone (same roof side, no major obstacles between pipes).
7. Run a cycle and check the seals.

More furnace guides

• Airflow lower than demanded, furnace runs on low stage when high stage is expected
• Alternate combustion air opening (upflow or horizontal)
• Alternate vent/flue location (upflow or horizontal left)
• Annual inspection checklist
• Auxiliary limit control (location and purpose)
• Auxiliary limit switch open (blower compartment)