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Why Is My Furnace Leaking Water?

Posted on: March 29, 2018

Water dripping from or collecting near your furnace is not something that should normally occur. If there are no plumbing leaks nearby that could explain the incident, it is possible that there is a problem with the furnace or related equipment.

Common Causes of Furnace Water Leaks

Furnaces do not use any water themselves, but moisture can be present in the combustion gases, condensing onto cooler surfaces if given the chance. If your HVAC system includes a humidifier, that can also be a source of moisture. Both can lead to leaks, and here are the most common causes:

  • Clogged condensate drain – If you have a high-efficiency, condensing-gas furnace, a clogged condensate drain is the most likely cause of the leak. Because these furnaces feature a secondary heat exchanger to extract as much heat as possible from the combustion gases, the vapors that are exhausted from the flue are relatively cool, allowing moisture to condense out of the gas. Normally, this moisture is channeled into the condensate drain, which empties into a plumbing drain or another suitable area. A clog in the condensate drain line will allow water to back up and leak from the furnace. If the system has a condensate pump, a pump failure can cause the same results.
  • Flue problem – If you have a standard, non-condensing furnace, a flue that is too large or not sloped properly can allow the exhaust gases to slow down and cool, releasing moisture. Because the flue on a standard furnace is metal, instead of PVC, this moisture can eventually cause other problems, like corrosion and flue leaks. Have the system inspected if you notice water leaking from the flue.
  • Humidifier problems – Because furnaces produce air that is relatively dry, humidifiers are often added to combat the irritation that dry air can cause. A leak or clog in the humidifier can allow water to leak onto or near the furnace. Have the humidifier repaired to avoid damaging your furnace.
  • Heat exchanger leak – If there is a leak in the secondary heat exchanger on a condensing furnace, moisture from the combustion gases can escape and create a leak. A damaged heat exchanger can also allow the combustion gases themselves to leak into your home, which can be dangerous. A leaking heat exchanger is less common than the other causes of water leaks, but it can be a costly repair and may require a complete system replacement.
  • Air conditioner leak – If the leak happens only when the air conditioner is operating, then the leak may be coming from a clogged condensate drain for the air conditioner or a clog in a drain line that is shared by both the furnace and the air conditioner.

To verify the exact cause of a water leak, you should have your furnace inspected by a professional. Water leaks can possibly damage the furnace, as well as porous materials located nearby, like drywall or insulation.

Furnace Repairs in the New Holland, PA Area

At The Witmer Company, we can help you determine the cause of the water leak and perform any necessary furnace repairs, including removing clogs from the condensate drain, replacing the condensate pump, and repairing the flue. Since 1941, we have been providing quality heating, air conditioning, and plumbing services to homeowners throughout New Holland, Lancaster, and the surrounding communities. Our friendly, certified technicians can help with any furnace problem you may have, from water leaks to heat exchanger failures.

To schedule furnace repairs in the New Holland area, contact us online or call 717-288-7163 today!

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