Why Is My Gas Furnace Leaking Water?

As your gas furnace runs, is there water leaking at the base? Is the furnace's air filter wet, too? There are a few things that could be happening here. But if you have a high-efficiency furnace, here's the most common cause: a condensation leak. We'll explain why a furnace creates condensation, and what's causing it to leak out of your furnace. Note: You'll know if you have a high-efficiency furnace if:

  • The yellow energy guide tag says your furnace's efficiency is 90% or higher AFUE.
  • The vent/flue pipe is white PVC as opposed to metal.

Why Do Furnaces Leak Water?

Furnaces produce water through combustion, and moisture in the air also forms condensation on them. Sometimes, the water can't escape or drain away as it should and it drips out or pools on the ground. Your furnace could be leaking for several reasons:

  • It's a high-efficiency gas furnace and condensation is leaking out or its drainage is blocked.
  • The flue on your standard-efficiency furnace is the wrong size.
  • Your whole-house humidifier is leaking into the furnace.

Why a high-efficiency furnace creates condensation

How in the heck does a high efficiency furnace create condensation/water anyway? It's all about how the furnace extracts heat from combustion gases. A lower-efficiency furnace extracts some heat from combustion gases and then quickly vents them out the flue pipe. But a high-efficiency furnace, to extract more heat, has 2 heat exchangers. These allow the furnace to extract heat from the gases for a longer period of time. This causes the combustion gases to cool and then condense. That condensation then exits out your home through a drain. But if that water is pooling around the furnace, there's a problem preventing it from draining properly. Causes of a condensation leak around a high-efficiency furnace

  • Clogged condensation tubing
  • Clogged condensation drain
  • Breaks in the condensation line
  • Issues with the condensate pump (if you have one)

You'll need a furnace technician to diagnose which of these is the issue and then fix it.

Other causes of leaking water around a furnace

If you have a conventional, standard-efficiency furnace

Then its flue pipe may be incorrectly sized.

If you have a whole-house humidifier connected to the furnace

There may be an issue which is causing the humidifier to leak into your furnace. Your humidifier should be getting annual maintenance from a professional to prevent this.

Is a Leaking Furnace an Emergency?

A furnace that's leaking water can be an emergency, if you're worried or feel unsafe, you should shut it down while you're waiting for a technician to fix the problem.

A leaking furnace isn't something you should ignore. Your home owners' insurance isn't likely to cover water damage due to lack of maintenance. If you can reach the puddle, mop it up and place a shallow tray underneath the furnace to catch the drips.

Can You Fix a Leaking Furnace Yourself?

A furnace leaking water could be a simple problem or a sign of a serious fault. Blocked drainage can redirect water where it isn't supposed to go—back into the furnace—and a leaking humidifier can destroy your furnace by causing an electrical fault. Another serious problem is a cracked condensation pipe, which can quickly turn into a big leak. This can be a serious problem especially if the furnace is laced in an attic or adjacent to a finished area of your home.

Need professional help in the Atlanta area?

Ragsdale has been serving the Atlanta area for over 25 years and can diagnose and repair your furnace leak issue. We'd be happy to help if you're experiencing issues with your furnace. And once the leak is fixed, make an annual service appointment. Regular servicing helps prevent leaks from reoccurring and keeps your furnace in top shape and operating at maximum efficiency.

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