Causes and Fixes for Water Heater Backdrafting


RepairYou can fix a simple water heater problem on your own. That may not be the case with complex problems though. An example of a complicated water heater defect is backdrafting.


This occurs when exhaust gasses from the heater spill out into the room. The gases contain carbon monoxide and high levels of moisture. A melted plastic, corrosion, and moisture at the top of the water heater are signs of backdrafting. Knowing the source of this problem is essential to prevent it in the future.

Causes and Fixes

Wrong installation of vent connector is a possible cause of backdrafting. The connector is attached to the vent, which provides means to release gases outside. Here are the three common mistakes in the installation of vent connector:

  • Incorrect Pitch. There must be a minimum slope of ΒΌ” per foot when installing the vent connector upwards towards the vent. It also should not sag or dip.
  • Insufficient Rise. Increase the rise in the vent if you have a 90-degree turn at the top of the draft hood and your connector only has minimum pitch.
  • Horizontal Run Too Long. It will be difficult for gasses to exit the vent with long horizontal run.

A problem with the vent itself can also be a reason for the backdrafting. For instance, using an oversized vent or chimney poses a problem to a relatively small burner. A small burner may not produce enough heat to warm up the entire vent. An obstructed chimney is another. Leaves and even dead animals can get stuck in the vent, blocking the airflow.

Check the combustion if the problem persists. You can also try opening a few more windows to give more air to the heater. According to All Hours Plumbing SLC, other water heater problems you must take notice of are leaks in the tube and discolored water.

To prevent water heater issues, have your system checked by plumbers regularly. Watching out for faulty parts and possible causes is a good preventive approach.