Stop
A damaged or disconnected vent can let carbon monoxide and combustion gases into the home; keep the water heater off and don't use it until the vent is repaired.
Symptoms
- Visible rust holes or flaking on the metal vent pipe
- Vent pipe sections not fully seated together or held with screws
- Soot staining near vent joints
- Vent pipe feels loose or wobbly when touched
Likely causes
- CommonAge-related corrosion of the metal vent pipeGalvanized vent pipe can rust through over many years, especially in humid environments.
- CommonSections not properly secured with sheet metal screwsLoose or unsecured joints can separate over time from vibration or age.
- PossibleIncorrect vent pipe slope or sizing causing condensation and accelerated corrosionImproper installation can lead to condensation forming inside the vent, speeding up rust.
What to do
- Turn off the gas water heater at the control valve before inspecting the vent closely.
- Visually inspect all visible sections of the vent pipe for rust holes, gaps, or disconnected joints.
- Check that each joint is overlapped in the correct direction (away from the water heater, toward the outside) and secured with screws.
- Do not attempt to patch a rusted vent pipe with tape or sealant; damaged sections need to be replaced with new vent pipe.
- Leave the gas water heater off and don't relight it until the venting is repaired if you find significant rust or disconnection.
- Have a professional inspect the full vent run, including the portion inside walls or the attic that you can't see.
Tools and parts
- Flashlight
Type B gas vent pipeSearch: “type B gas vent pipe water heater”
When to call a pro
Have a licensed plumber or HVAC technician replace the damaged vent sections and verify proper slope, connection, and termination.
Safety
Stop
A damaged or disconnected vent can let carbon monoxide and combustion gases into the home; keep the water heater off and don't use it until the vent is repaired.