Why Is Water Coming Out of My Furnace?

Why Is Water Coming Out of My Furnace?

Is water leaking out of your furnace? Don’t worry! Read on to troubleshoot the issue.

First, determine if your furnace is a conventional furnace or a  high-efficiency condensing furnace. Here’s how to tell:

Do you see a metal vent pipe coming out of the side or top of your furnace? You have a conventional furnace.

Do you see a white PVC vent pipe coming out of the furnace side or top? If so, you have a high-efficiency condensing furnace.

Why is My Conventional Furnace Leaking Water?

If your conventional furnace is leaking water, the most likely reason is:
• Leaky humidifier
• Improperly designed vent pipe
• Furnace is leaking because the AC is on

How to Determine If You Have a Leaky or Clogged Humidifier

If your furnace has a built-in humidifier, the humidifier may be clogged or have a leak. This could explain why water is pooled around your furnace. Humidifiers require water to create humidity, so water continually flows into it and drains from it, adding moisture to the air in your home.

• Check your furnace to see if there is a built-in humidifier. The humidifier is typically visible on the outside of the furnace.
• Look for leaks or a clog at the tap line, drain line, water feed, and the humidifier’s outside casing.

Call a pro if the humidifier is leaking water or appears clogged.

How to Figure Out If Your Water Issue Is the Result of a Faulty Furnace Vent Pipe

Conventional furnaces have metal flue pipes. The flue pipe carries gases produced during the combustion away from your home. If your furnace is working correctly, those gases escape outdoors before they have time to cool down and condense into moisture.
However, if the exhaust pipe is too big or has an incorrect slope, this allows too much air to circulate and traps gases inside the flue. As gases sit in the flue, they cool, and form condensation. This condensate may leak out of your furnace in the form of water.

To determine if the issue is the vent pipe, follow these steps:
• Look at your flue pipe. Is water leaking from it?
• Is there little or no slope to the pipe?

Contact a heating professional if you answered “yes” to either of those questions. They will inspect your vent pipe to ensure it has a diameter and design that matches your furnace and can repair any leaks.

How to Determine if it’s the AC

Is the furnace leaking water only when the AC is on?
If your furnace seems to only leak when the AC is running, the problem most likely is not your furnace, it’s your AC. Your AC doesn’t just cool your home. As the AC runs, it absorbs moisture from the warm air and dehumidifies your home. The moisture usually drains out of your home via a condensate drain line. However, if the drain line is clogged or there’s a leak in the line, pan or the AC itself, water can leak into the surrounding area.

So look at the drain line on top of, or next to your furnace. It may appear as if the furnace is leaking water when it’s actually a leaky or clogged AC drain line.

Why Is My High-Efficiency Condensing Furnace Leaking Water?

It’s normal for high-efficiency furnaces to create condensation during operation. That is why it’s called a “condensing furnace.”

The most common reasons that condensing furnaces to leak water include:
• Blocked condensate drains
• Condensate pump problems
• Condensation line issues

Why High-efficiency Furnaces Produce Water

High-efficiency furnaces have two heat exchangers. The two heat exchangers absorb heat, causing the exhaust gases to change from a gas to a liquid state. Condensation forms and drains out through the condensate line.

This type of furnace should be serviced regularly so it can drain the water that condensates. If there’s a clog or a leak, the condensation can’t be carried out and ends up pooling around the base of your furnace.

What to Check on a High-Efficiency Furnace

Check the drain trap. Is it clogged? Over time, the drain trap will collect dirt and water. If it’s clogged, use a shop vac to clear it.

If the condensate pump, humidifier, or drain line is broken, schedule a repair.

If you’ve gone through this entire checklist, and you’re still not sure about why water is coming out of your furnace, call a heating professional to diagnose and fix the issue.

If you live in the Rockland County New York, Orange County New York or Bergen County New Jersey area, CV Plumbing, Heating, AC and Pools can conduct a furnace inspection for you.

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