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Why Is My Furnace Leaking Water?

Is there water leaking at the base of your furnace? Don’t panic. 

The most common reason for furnace water leakage is because it’s high-efficiency and has one of these issues:
  • Blocked condensate drains
  • Condensate pump problems
  • Issues with the condensation line

In this article, we’ll:
  • Show you how to determine if you have a high-efficiency furnace
  • Explain why high-efficiency furnaces create water
  • Describe how to fix the above-mentioned problems

How can you tell if your furnace is high-efficiency vs. standard-efficiency? 

Your vent pipe should be made of white PVC or ABS plastic. Standard efficiency furnaces would have a metal vent pipe.

Another easy way to check is to look at the yellow energy guide tag on your furnace. Your furnace efficiency should have a 90% or higher AFUE rating. 

Why do high-efficiency furnaces create water? 

High-efficiency furnaces create water because they have two heat exchangers, one more than a conventional furnace. The two heat exchangers absorb so much heat that the exhaust gas changes from a gas state to a liquid state. Condensation forms and then drains out through the condensate line.

Your furnace must be properly serviced so it can properly drain the water that condensates. If there’s any leak or clog, the condensation can’t be carried out of your home and ends up pooling around your furnace. 

What if I don’t have a high-efficiency furnace and there’s leakage? 

If your furnace is leaking and it’s not high-efficiency, here are a few reasons why it could be leaking: 
  • Furnace humidifiers use tap water to create moisture in your air. If there’s a humidifier crack or leak, then the tap water will start dripping around your furnace. 
  • Sometimes leakage isn’t even the fault of the furnace! If you use your A/C along with your furnace during certain times of the year, the A/C can end up leaking onto the furnace. 
  • If you have a standard-efficiency furnace, double check that your vent pipe is correctly sized. The vent pipe should have a diameter that matches the furnace. If it’s too small or too large, it won’t be able to support the amount of combustion gases generated by the furnace.

How do I fix this leak? 

Your high-efficiency furnace is leaking. Now what? Check the drain trap first. The drain trap collects dirt and water over time. If it’s clogged, you can use a shop vac to clear it.

But if the condensate pump, humidifier, or drain line is broken, you’ll need to schedule a repair with a technician.

If you’re not sure about the cause, one of our expert technicians can diagnose your furnace for you. Schedule a diagnosis today if you live in our service area.

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