Join QRC in the Fight Against Breast Cancer!

Post a Pic, Get a FREE A/C Tune-Up!
+ Enter $200 Giveaway

Join QRC in the Fight Against Breast Cancer!

Post a Pic, Get a FREE A/C Tune-Up!
+ Enter $200 Giveaway

Home > HVAC > Why Is My Furnace Leaking Water?

Why Is My Furnace Leaking Water?


You probably found this page because you typed “Why is my furnace leaking water?” – or something along those lines – into the Google search bar. Chances are, you’ve noticed a puddle around your furnace system and are now imagining yourself on a boat, in a building full of water because you don’t know how serious this leak could be!

First, you need to find out what’s causing the leak. More than likely, you won’t end up on a boat in your living room.

To determine what could be causing the buildup of condensation on your furnace, it’s important to know whether or not you have a high-efficiency furnace or a standard efficiency furnace.

How Can I Tell If My Machine Is High-Efficiency or Not?

You have a high-efficiency furnace if:

  • The flue pipe, or vent, is made of white PVC instead of metal.
  • Your furnace’s efficiency is 90% or higher AFUE, which you can find on the yellow energy guide tag.

If I have a High-Efficiency Furnace, why is it leaking water?

If you have a high-efficiency furnace, the most common cause of water is a condensation leak.

A high-efficiency furnace has two heat exchangers to extract more heat than a lower-efficiency furnace. That way, the furnace can extract heat from the combustion gases for a longer period of time. Since they’re being cooled for longer periods of time, the combustion gases cool and then condense.

Typically, that condensation is routed to exit your buildilng via a drain, but if you notice pools of water around your furnace then there may be an obstruction or other problem preventing the condensation from draining as it should.

Typically a condensation leak is caused by clogged condensation tubing, breaks in the condensation line, a clogged condensation drain, or an issue with the condensation pump (if applicable).

If I have a Lower-Efficiency Furnace, why is it leaking water?

There are a few reasons your lower-efficiency furnace may be leaking water:

  • A flue pipe could be incorrectly sized on your furnace.
  • Do you have a humidifier connected to your furnace? If you do, the humidifier could be leaking into your furnace.


Regardless, never try to fix any of these problems on your own! If you notice water pooling around your furnace, call QRC immediately so we can diagnose the problem and fix your furnace!