Skip to Content

Water Leaking From Furnace? Here’s What To Do

Why would water be leaking from my furnace?

When it comes to issues around your furnace, you want to deal with them immediately. When we saw that there was water leaking from our furnace recently we knew that we need to have it looked after but before you call a heating and cooling professional it’s good to know that there are several reasons water may be leaking from your furnace and not all of them require a house call.

These are the steps you should take before you contact a furnace repair person. Often the issue is one of these items that you can deal with on your own, saving you a house call and money in the process.


Here are the possible causes water is leaking from the furnace

Check for a Plumbing Leak

When the furnace is leaking, it’s a good idea to inspect around the area to make sure that the water is indeed coming from the furnace and not another part of the area that the water drained from. Inspect the area to make sure, in fact, that your furnace is leaking.

Often we will see water on the ground by the furnace and not think to look up. There may be a leaking water line in the house that is causing the water to pool around the furnace. This means you don’t need a furnace maintenance specialist but a plumber to address the leak. For example, a leaking flexible hose line under your sink could trickle down the pipe and be dripping in the area.

It’s a good idea to inspect your water heater for leaks, check to make sure there is no water leaking from the bottom of your water heater, and that there is no leaking from the top of your hot water tank.


Look for a Condensation Leak

Often when there is water leaking from the furnace, it’s caused by a condensation leak. This can happen when your high-efficiency furnace extracts the heat from the combusting gases and then cools. This causes condensation, which should be routed to a drain via PVC pipe.

If condensation is the cause of the water, then there are a few reasons that this could be happening for one of two reasons.

Note: if you smell gases, it could be that your heater exchanger cracked, in which case you have a separate issue.

Blocked Drain Pipe

The extra water should be drained via a pipe coming out of the furnace and going into a drain. Over time the pipe can get clogged, and if the water has nowhere to go, it will back up and leak out of your furnace.

Broken Pipe

Another reason could be that the pipe is broken. Inspect the pipe to see where the water is leaking and see if there is a crack in the pipe.


Is the Air Filter Clogged

If you haven’t cleaned your air filter recently, this may be the culprit. Cleaning or replacing your furnaces air filter should be part of your regular household maintenance schedule, but because it’s out of sight, it’s usually out of mind.

Inspect the filter to see if it is clogged. A clogged air filter could cause a leak, and then water would become visible around the base of the furnace.


Examine the Air Conditioner

Your air conditioner may be the reason for the water leaking out of your furnace. If you are in a part of the country that has you running the furnace and A/C on the same day, the water from the condensation pan may be full and dripping onto the heating system. This means the furnace isn’t the issue, but instead, it’s the air conditioner.

Check to see if your furnace and air conditioning share a drain and line to see if it is clogged.

See if this is the case and if not, proceed to the next step.


Look at the Humidifier for Leaks

If you have a whole-house humidifier in your room, this may be the reason for the water. These units are connected to the furnace, and it could be leaking in to the furnace and be the cause of the leaking furnace. Because these items are installed into the plumbing system, if there is any clog or break in the line, there will be water by your furnace.


Check the Secondary Heat Exchanger

If you have tried all of the above and still can’t find where the water is coming from, it may indicate a problem with the heat exchanger. This type of problem can be the source of your water issues and will need to be repaired. If it turns out to be the secondary heat exchanger, then your furnace may need to be replaced.

You will need to contact a repair person to come out and inspect the furnace to see if this is the issue.


Leaking Furnace FAQ

Is water leaking from the furnace dangerous?

A leaking furnace can be a dangerous issue, or it may not be related to the furnace at all. Inspect the furnace and contact a local tradesperson to service your furnace immediately.


How do I fix a leaking furnace?

A leaking furnace can be one of several reasons. If you have exhausted all of the simple solutions that you can do on your own, the next step is to contact a licensed repair person.


How much does it cost to fix a leaking furnace?

Depending on what the issue is, it could range from a short visit to a complete replacement of the furnace, as is the case with a leaking secondary heat exchanger.  To get a better idea of pricing, contact a local furnace repair technician as it can range across the country.

Read More About Water Issues:


What to do when you notice water leaking from a furnace

If you cannot identify the issue and where the leak is coming from, you need to contact a licensed repair person. Water leaking from your furnace is an issue that needs to be dealt with immediately. If you can shut it down, it is best to do so while waiting for the technician to arrive.


Click Here to Find a Professional 

This post may contain affiliate links which go towards keeping this site running. Please see our Disclaimer and Privacy Policy for more. We are a member in the Amazon Affiliate Program. Thank you for your support!