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Why Is My Furnace Leaking Water?

Closeup of a water puddle on a concrete floor

A cozy home with a reliable heating system is a welcome retreat, especially during the colder months. However, discovering that your furnace is leaking water can be a cause for concern and confusion. In this blog, we'll delve into the most common reasons behind why it happens, as well as explore potential solutions to help you restore your furnace to optimal performance.

Want to avoid furnace issues altogether? Check out our blog, “What Is Heating System Maintenance And Why Do I Need It?” to learn more about how regular furnace tune-ups can prevent problems like leaking water.

Is your furnace leaking water? Don't wait – contact the professionals at Comfort Systems for expert furnace repairs.

As a locally owned and operated business for more than 55 years, our skilled technicians have the expertise to diagnose and fix any furnace problem you have. Plus, we offer convenient same-day service, including 24/7 emergency service!

Condensation Issues

One of the primary reasons your furnace might be leaking water is condensation. High-efficiency furnaces extract more heat from the combustion process, producing a significant amount of water vapor. In a well-functioning system, this moisture is typically drained away. However, if there are issues with the condensate drain line or trap, water can accumulate and cause leaks.


Inspect the condensate drain line for clogs and clean or replace it if necessary. Ensure that the drain trap is functioning correctly and that the water is effectively draining away from the furnace. Regular maintenance, including cleaning the condensate system, can prevent future issues.

Cracked Heat Exchanger

A cracked heat exchanger is a serious problem that can lead to water leakage in your furnace. The heat exchanger is responsible for transferring heat from the combustion process to the air circulating in your home. If it develops cracks, water produced during combustion can leak out and pool around the furnace.


Unfortunately, repairing a cracked heat exchanger is not a DIY task. It requires professional intervention. A certified HVAC technician can assess the extent of the damage and recommend either repairing or replacing the heat exchanger. Ignoring this issue could lead to the release of harmful gasses into your home, making prompt action crucial.

Clogged or Disconnected Drain Line

The drain line in your furnace is designed to carry away condensate produced during the heating process. If this drain line becomes clogged or disconnected, water can accumulate and result in leakage.


Check the drain line for any visible clogs or disconnections. If you find any issues, carefully clear the blockage or reattach the line. Regularly inspecting and cleaning the drain line can prevent future problems.

Humidifier Issues

If your furnace is equipped with a built-in humidifier, it could be a potential source of water leaks. A malfunctioning humidifier may allow excess water to accumulate, leading to leaks around the furnace.


Inspect the humidifier for any visible issues, such as leaks or clogs. Ensure the water supply is connected correctly and the humidistat is functioning properly. If you encounter problems, consult your furnace manual or contact a professional for assistance.

Faulty Secondary Heat Exchanger

Inspect the humidifier for any visible issues, such as leaks or clogs. Ensure the water supply is connected correctly and the humidistat is functioning properly. If you encounter problems, consult your furnace manual or contact a professional for assistance.


Again, addressing problems with the secondary heat exchanger requires the expertise of a trained technician. They can assess the condition of the heat exchanger and recommend repair or replacement as needed.

Incorrect Venting

Proper venting is crucial for the safe operation of your furnace. If the vent pipe is improperly installed or damaged, it can allow water to enter the system and cause leaks.


Inspect the vent pipe for any visible damage or incorrect installation. Ensure that it slopes away from the furnace to allow proper drainage. If you notice any issues, seek professional assistance to correct the venting problems.

Air Conditioning Coil Leaks

In homes with a combined heating and cooling system, the air conditioning coil is housed within the furnace. If the coil develops leaks, water can accumulate and lead to leakage.


A professional HVAC technician can inspect the air conditioning coil for leaks and recommend appropriate repairs. Regular maintenance of both heating and cooling components can help prevent such issues.

Don't let a leaking furnace compromise your comfort – trust Comfort Systems of York County for unparalleled furnace repairs.

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Our seasoned technicians know their way around all types of furnaces, regardless of the make, model, or brand. Rest assured, your leaking furnace will be in capable hands as we efficiently diagnose and address the issue. Schedule your service today and see for yourself why we’ve earned hundreds of 5-star reviews from satisfied customers throughout Rock Hill and beyond.