Fix-It Chick: Properly vent a natural gas water heater

Chances of carbon monoxide poisoning rise during the winter months when a home is sealed tight. Checking and correcting a natural gas water heater vent is a simple step toward preventing the back draft of fumes into your home.

Step 1: Rust stains, corrosion, melted plastic or condensation found on the top of a water heater are signs of an improperly vented system. Test for back drafting by turning the hot water on in a nearby tub or sink. When the water heater kicks on, cup your hands a few inches from the vent opening at the top of the heater. Do not touch the vent pipe. If you feel warm, moist air on your hands, the heater is not venting properly.

Step 2: Confirm the vent hood is properly positioned directly above the vent hole on the top of the water heater. The vent hood should be standing on three straight legs. If the legs are bent or broken or the hood is rusted through, repair or replace the vent hood immediately.

Step 3: Securely attach galvanized vent pipe to the vent hood with three rust-resistant screws. Use a stove pipe increaser to attach larger vent pipe. Never use vent pipe smaller than the vent hood opening.

Step 4: Single-wall vent pipe requires 6 inches of clearance from combustible materials, such as drywall, wood and other building materials. If vent pipe passes through a wall, ceiling or an inaccessible or unheated area double wall, type B vent pipe should be used instead of galvanized pipe.

Step 5: Vent pipe runs should be as short as possible and must rise vertically from the water heater. For horizontal runs, a minimum rise of 1/4 inch per foot is required for proper venting.

Step 6: Single-wall galvanized vents should be secured together using three rust-resistant screws at each joint. Do not seal joints with duct tape or other sealant products. Double-wall type B vent pipe sections that lock together do not require additional fasteners.

Step 7: Check existing vent pipe for corrosion or damage. Ensure the pipe is secured at each joint and the rise of the pipe is sufficient enough to avoid condensation damage along the run.

Step 8: Check the exit point of the vent pipe on the exterior of the home. Confirm the pipe is free from obstructions and is protected with a properly fitted vent cap.

— Have a home improvement question you want answered by the Fix-It Chick? Email it to Linda Cottin at


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