Water Heater Backdraft

Sometimes combustion gases that backdraft into a house leave soot.

Water heater backdraft.

Inspectors should be properly trained to use these before they attempt to use one during an actual inspection primarily to avoid false negatives. Insufficient combustion makeup air is a condition that many plumbers and hvac folks seem to have a tough time diagnosing. A common source of backdrafting is orphaned water heaters. This problem affects mainly the atmospheric gas type water heaters that use the natural convection for the removal of the products of combustion known as the exhaust gases.

Even in a home with a water heater that drafts very well just throw in a big 600 cfm kitchen hood fan and it s almost a guarantee that the water heater will backdraft with the fan running. When homeowners replace older furnaces with more efficient models that don t use the chimney to vent gas water heaters are often left as the only device venting into the chimney which is now oversized for the water heater alone. Proper venting prevents backdrafting. A carbon monoxide analyzer can be used to test for backdrafting of that gas.

The simplest way to prevent backdrafting is to provide a source of replacement air also called combustion air for your furnace water heater and fireplace to replace the air that flows up the chimney with the exhaust fumes fig. Look for a dark residue on the top of your water heater. The most common problem associated with water heater venting is a condition called backdrafting in which exhaust gases from the water heater fail to exit the home via the vent and instead end up in the house. The main reasons for the backdrafting at the water heater are the poor vent installation and the obstructions found in the vent pipe.

Backdrafting at a water heater is a common defect identified during home inspections and it s almost always a condition that the homeowner or occupant is not aware of. Even in a home with a water heater that drafts very well just throw in a big 600 cfm kitchen hood fan and it s almost a guarantee that the water heater will backdraft with the fan running.