Heating Contractor Explains Back Drafting

Back drafting is the reverse flow of exhaust gases in a flue or chimney. Rather than going outside, the gases enter the home. Breathing these gases can cause weakness, sickness, and may even cause death. These combustion gases may contain carbon monoxide, which is an invisible, odorless, and deadly gas. Back drafting can be a problem with older appliances that rely on the natural buoyancy of hot exhaust gases to rise up the flue or chimney and out of your home.

Three Causes of Back Drafting

Your Home Is Too Airtight

Sealing up your house to reduce home heating bills saves heating fuel and is environmentally sound. However, too much of this can cause problems when exhaust fans, dryers, and fireplaces (with a fire) create a partial vacuum in your home. This may draw air into your home through the furnace/water heater flue and pull exhaust gases inside. Sometimes smoldering wood in your fireplace produces insufficient updraft to overcome the suction produced by your fans, and a back draft will come into your house through the fireplace chimney and draw the smoke inside.

You Have an Orphaned Water Heater

If you recently installed a furnace that has its own venting, and the previous furnace shared a flue with your water heater, then the water heater is "orphaned." Without the "assistance" of your previous furnace, the heated exhaust from the water heater isn't enough to overcome the dense cold air in the flue. The water heater exhaust gas flows into your home instead.

You Have Problems with Your Flues or Vent Stacks

Back drafting can occur when your flue is partially clogged with debris or other obstructions. The exhaust gases, seeking the path of least resistance, will flow into your home instead of going up the flue. Vent pipes with leaks or with a downward slope will also cause this problem.
Signs of back drafting include rust on the grillwork of your furnace and rust on the top of your water heater. This rust is caused by the water vapor in the exhaust gases. If you see water condensation on nearby plumbing on a dry winter day, and you have no other known moisture sources, back drafting is a likely suspect.

Back drafting is a serious safety concern. If you think you have this problem, ask a qualified Ocean City NJ heating repair expert to correct the problem as quickly as possible.