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Can a Dirty Filter Really Cause Water Leaks in a Furnace?

March 2, 2015 | Blog

If you’re trying to find the cause of a water leak in your furnace, it’s not unreasonable to try changing your air filter. A clogged filter can’t directly cause water leaks in a furnace, but it can contribute to leaking air conditioner problems if they share the same ductwork.

Many central air conditioning systems are installed with the evaporator coil sitting on top of the furnace inside the main supply duct. A dirty furnace filter can restrict airflow across the evaporator coil, resulting in excessive moisture and freezing temperatures that can result in ice buildup on the coil. When your A/C turns off, the ice can melt and drip down into your furnace if the condensate drain can’t handle all of the moisture.

Changing your furnace filter might allow sufficient airflow in your ductwork to keep excessive moisture from accumulating on the evaporator coil. If you see that water is still dripping from your furnace after you’ve changed the filter, or if you detect corrosion on any of the metal parts in your HVAC system, ask your HVAC technician to look for the moisture source. Some other potential sources of water leaks in a furnace, include:

  • Ineffective venting of combustion gases. Water vapor is one of the main combustion products vented from your furnace to the outside of your home. If the gases are not vented efficiently, water can condense inside the vent flue and run back down into the furnace. This can be a problem with high efficiency condensing furnaces if the condensate drain tube is not securely connected.
  • Leaking humidifiers. Humidifiers aren’t usually necessary in our humid Coastal Bend climate, but if your HVAC system has one, it could develop a leak in the water line that supplies the humidifier.
  • External leaks. Don’t overlook the possibility of leaks in your roof or plumbing that might drip water onto your furnace.

Call CCAC for help finding and fixing water leaks in your furnace. We serve homeowners throughout the Corpus Christi area.

Our goal is to help educate our customers in Corpus Christi, Texas about energy and home comfort issues (specific to HVAC systems). For more information about furnaces and other HVAC topics, download our free Home Comfort Resource guide.

Credit/Copyright Attribution: “Serenethos/Shutterstock”

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