Why is My Furnace Leaking Water? 5 Reasons Why

The water around your furnace isn’t normal and can lead to rust, mold, mildew, and damage to your floors.

Your furnace leaking water means you’re having issues with:

  • condensation leak
  • humidifier leak
  • filter is clogged
  • damaged heat exchanger
  • clogged drain line
  • the condensate pump is clogged
  • plumbing leak

Below you’ll find out more about the reasons why your furnace is leaking water and how to fix it.

Let’s get started.

5 Reasons Why Your Furnace is Leaking Water

Before you continue, it’s important to distinguish if your furnace is leaking when the AC is on, because that is a separate issue you should investigate independently.

1. Condensation leak

Most furnaces today operate with two heat exchangers which can result in condensation.

The condensation is then drained through the pipes in your home.

This water normally is sent into a floor drain, but if there is a broken pipe or a clog, you’ll be sure to notice your furnace leaking.

This is a major problem that must be serviced ASAP, don’t wait until the problem is much larger and more expensive to fix.

2. Humidifier leak

If you have a humidifier hooked up to your furnace, it’s possible that the culprit is your humidifier.

Your humidifier will have a water line attached to it as well as a drain to get rid of any excess water.

Moisture buildup can cause a leak to occur in your furnace caused by a clog in the lines or your humidifier has a broken part that needs to be serviced.

You can learn more about furnaces with humidifiers here.

3. Filter is clogged

A clogged filter is another reason why your furnace is leaking water.

Over time, your filter can become clogged which can cause restricted airflow.

Restricted airflow can lead to your coils freezing over which will result in your furnace leaking water.

Ensure that you’re using a clean filter and the coils aren’t frozen over. If they are, let the coils defrost and then continue using your furnace.

4. Leaking in plumbing

Be sure that the water is coming from your furnace and not the surrounding plumbing.

It’s possible that the leak is coming from the ceiling or any pipes that you may have in the same room your furnace is in.

If you do manage to spot the leak, ensure that it isn’t connected to your furnace.

It could also be that if you have a furnace and air conditioner that your air conditioner is causing condensation and not your furnace.

5. Damaged Heat Exchanger

A damaged heat exchanger can cause carbon monoxide leaks as well as cause leaks.

Not every furnace will have moisture inside the heat exchanger (high-efficiency furnace).

If you have a high-efficiency furnace, then you may have an issue with your secondary heat exchanger.

If this is the case, then you may have to replace your furnace.

It’s best to have a licensed HVAC technician inspect your heat exchanger if you aren’t sure how to do it yourself.

Clogged drain line

When water is drained from your furnace, it must go through a condensate drain line.

Over time, loose connections, cracks, or holes can cause your condensate drain line to leak. It may also get clogged over time from years of use.

A clogged drain line can also cause your furnace to blow cold air.

The condensate pump is leaking

A condensate pump is what is used to pump the water out of your furnace. The condensate pump may be clogged which will cause your furnace to leak.

If you’re finding water around the floor of your furnace where the condensate pump is located, then it’s likely you have a problem with the condensate pump.

Should You Call an HVAC Technician?

While a small furnace leak may seem insignificant, over time, constant exposure to water can cause mold, mildew, and even damage to your home.

A leaky furnace may also be a sign that your furnace must be serviced. If rust is left to develop on the internals of your furnace, you may end up having to replace your entire furnace if a problem should arise with your heat exchanger.

It can also be dangerous as well, so if you notice water around your furnace, then it’s best to call an HVAC technician to service your furnace as soon as possible.

About Roy Cohen

Roy Cohen has a burning passion for heating, cooling, and ventilation. He aims to help you save money on expensive repairs and bring you the best HVAC products. He has years of experience behind him in HVAC repair and garage maintenance.

You can find Roy at his LinkedIn or his email: [email protected]

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