Should You Be Worried About Gas Water Heater Backdrafting?
To borrow from a classic public service announcement – it’s 10 p.m., do you know where your water heater exhaust gases are? Admittedly, that phrase isn’t quite as memorable, but it’s still very important for homeowners to be aware of a water heater issue called backdrafting.
Backdrafting is a dangerous situation where toxic combustion gases are not properly vented. Instead of rising up through a chimney and releasing outside, some exhaust gas enters the home. Backdrafting is primarily a concern with atmospheric venting gas water heaters.
Why does backdrafting occur?
With an atmospheric venting water heater, hot exhaust gases are designed to naturally rise and go out of the chimney. If the vent was installed incorrectly, such as the vent pipe having too many angles or a downward slope, the exhaust gas will not reach the top of the chimney on its own. Furthermore, if there’s a blockage in the vent, this could force the exhaust gases down the pipe and into the home.
Testing for backdrafting
The good news is that backdrafting is relatively easy to test or recognize. Here are a few methods.
- Cup your hands around the draft hood (the cone-shaped vertical pipe at the top of your water heater) and see if you feel warm, moist air
- Place a small mirror by the draft hood, and check back to see if the mirror fogs, which would indicate the presence of moist air
- Inspect the draft hoot for soot, which is a dark residue
- Check to see if the plastic cap on top of the water heater is melted or deformed
- Look for corrosive stains on the top of the water heater, which would be caused by condensate from the exhaust; likewise, if you see water/moisture on top of the tank, this could be from backdrafting
What to do if you have backdrafting
If you find evidence of backdrafting or suspect that your water heater is leaking exhaust gas into your home, do not ignore this problem. The most immediate thing you can do is improve the ventilation in your home by opening the windows or running a nearby exhaust fan, such as in a bathroom or kitchen. Next, call an experienced HVAC technician to look at your water heater and see what can be done. It may be possible to correct the ventilation setup, replace a missing vent cap, or install a power vent.
Is it time for a new, safer water heater?
Depending on the age of your water heater, you may want to consider replacing the unit. Atmospheric gas water heaters are usually entry-level units. A safer choice may be a power venting water heater with a fan that helps push the combustion gases out of the home, instead of relying on the natural rise of the gases. This type of venting greatly reduced the chance of backdrafting.