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Top Reasons Why Your Furnace is Leaking Water

As outside temperatures cool down, it’s common for homeowners to take stock of their heating system and make sure, “everything looks okay.” And then often what begins as a basic furnace inspection ends with a nervous phone call to our office with the same common question, “Why is my furnace leaking water?”

While there are a variety of explanations for this, we compiled a list of the most common reasons:

Condensation leak. If you have a high-efficiency furnace, it will create condensation as it utilizes cool exhaust and then pipes it away from your unit. If your tubing is damaged, broken or not functioning properly, then this could be the cause of your leak. Another reason for the leak could be due to a clogged drain.

Standard efficiency furnaces, on the other hand, should not have condensation, so a leak is particularly unusual and could signal an improperly sized flue pipe. If this is the case, then hot exhaust might be condensing in the pipe as it cools down.

How do you know if your furnace is high- or low-efficiency? Take a look at the vent pipe; if it’s PVC (white plastic), then it’s a high-efficiency unit. Standard-efficiency furnaces have metal exhaust pipes.

Secondary heat exchanger. If furnace condensation isn’t the problem, the leak might be caused by the secondary heat exchanger. Unfortunately, this is a very expensive repair, and most customers decide to just replace the furnace as opposed to repairing the problem.

Humidifier leak. Another reason for the leak could be due to a faulty humidifier. If you’ve stayed on top of your annual HVAC maintenance, then this probably isn’t the issue because your service technician most likely would have noticed the problem. If you’re behind on service, schedule an appointment immediately because this type of leak could cause serious damage to your unit.

Internal drain system clog. One final cause for the leak could be due to a plug in the internal drain system that operates in both the air conditioning unit and the furnace. If it’s plugged, it could be directing water into the furnace.

Whatever the cause, you will need a specific diagnosis for the leak in your furnace. Don’t ignore the problem, as leaks can cause significant damage to parts, walls and flooring, and can lead to harmful mold growth. Indianapolis area homeowners can contact us at 317-451-4371 and we’ll be happy to discuss your leak or schedule a furnace service call as soon as possible.