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Why Is My Furnace Leaking Water?

Is water leakage at the base of your furnace putting you at risk of dealing with potential water damage in your home? No need to panic – this issue is more common than you may think, and the knowledgeable team of technicians at Action Air is here to help.

What to Look for First

In order to determine potential causes of the water leakage, you must first determine whether you have a high-efficiency condensing furnace or a conventional (non-condensing) furnace. This is something you can tell from a glance by looking for the following:

-A white PVC vent pipe coming out of the side or top of your furnace means that you have a high-efficiency condensing furnace.

-If you just see a metal vent pipe, then you have a conventional furnace.

Do you have a high efficiency condensing furnace that is leaking? If so, read our first section entitled, “Why your high-efficiency condensing furnace is leaking water.”

Do you have a conventional furnace that is leaking? Skip to the second section entitled, “Why your conventional (non-condensing) furnace is leaking water”.

Why Your High-Efficiency Condensing Furnace Is Leaking Water

So, now that you have successfully determined that you have a high-efficiency condensing furnace, you can enjoy a big sigh of relief! During the operation process it is normal for condensation to form, meaning the water leakage is most likely going to require a minor repair.

“But why is the condensation leaking into my home?,” you ask? Here are the most common causes:

-Problems with the condensate pump

                -Blocked condensate drains

                -Issues with the condensation line

In order to pinpoint the cause of the water leakage, it helps to understand how a high-efficiency condensing furnace works during this operation process. In this section we will explain why and how high-efficiency furnaces create water, and how that water is carried away from your home.

High-Efficiency Furnace Operation Process

As is reflected in the name, a high-efficiency condensing furnace creates water from the condensation that forms when the two heat exchangers absorb so much heat that the exhaust gas changes to a liquid state. When working properly, the condensate then carries that liquid outside and away from your home.

If you have a high-efficiency furnace, it must be regularly serviced so it can continue to drain properly. Any leak or clog in the condensate line will eventually lead to water leakage inside your home.

How Do I Fix This Leak?

So, your high-efficiency furnace is leaking – now, how do you fix it? First, check the drain trap to see if it is clogged. Over time, dirt and water collect within the drain trap. If your drain trap is clogged, use a shop vac to clear it out.

If your drain trap is not clogged, or the leakage continues after clearing it with a shop vac, you may have a damaged condensate pump, humidifier, or drain line. If this is the case, you will need to schedule a repair with a technician.

Even if you are not sure what the cause might be, any one of our experts at Action Air can diagnose your high-efficiency furnace for you and handle any repairs that may be required.

Why Your Conventional (Non-Condensing) Furnace Is Leaking Water

Even though you have a non-condensing furnace, the root of the water leakage will still be condensation. However, there could be 3 different sources of the condensation:

  1. Leaky humidifier
  2. Vent pipe
  3. Air Conditioner

Leaky Humidifier

If the built-in humidifier within a conventional furnace is clogged or has a leak in it, that may be the cause of the water leaking into your home.  Not all conventional furnaces have built-in humidifiers, so your first step in ruling this out as a cause of the leakage will be determining whether your furnace has one.

To determine if a built-in humidifier is the cause, follow these steps:

  1. Look at your furnace to see if you have a built-in humidifier. The humidifier is typically visible on the outside of your furnace and should be easy to detect.
  2. Once you find the humidifier on your furnace, look for any leaks or a clog at the drain line, water feed tube, and the water tap line. You should also look for any leaks on the outside casing of the humidifier.
  3. Call a professional if the humidifier is leaking or clogged for an official diagnosis and repair.

Don’t think the humidifier is the culprit? Then read on to the next section.

Improperly Sized Vent Pipe

Unlike a high-efficiency condensing furnace, a conventional furnace has a metal flue pipe that is designed to safely carry away gases out of your home during the combustion process, before they have time to cool and condense into liquid form.

If your vent pipe has no slope or is too large, it causes gas to become trapped inside the flue when too much air circulates. When the gas is inhibited from escaping, it gathers inside the flue and cools, eventually forming condensation. This condensation can leak out of your furnace into the surrounding area, bringing water leakage into your home.

To see if the vent pipe is the source of the leakage, follow these steps:

  1. Examine your flue pipe. Do you see water leaking from it? Or is there no slope?
  2. If your answer to either or both questions was “yes”, contact a professional to inspect your vent pipe to verify that the design and diameter measurements fit your furnace. Any leaks can also be repaired during this visit.

Don’t think that your vent pipe is the source of your water problem? Then keep reading…

Air Conditioner

So, now you have examined your furnace for potential humidifier or vent pipe damage and have yet to find the source of the water pooling in your home. If that is the case, then the cause of the water leakage is most likely not your conventional furnace, but your AC.

Your air conditioner, in addition to cooling your home, dehumidifies it. This means that your AC is absorbing moisture from the warm air in your home while it runs.

When everything is working efficiently, the moisture from the condensation should drain out of your home through a condensate drain line (the white PVC pipe that surrounds the metal flue). If there is a clog or leak in the drain line, drain pan, or the AC itself, water can start to leak into the surrounding area and into your home.

So, how do my AC problems account for my furnace leakage?

That drain line that we previously mentioned that might be leaking condensation from your AC is typically sitting directly on top of or next to your furnace, making it seem like the source of the water leakage is your furnace, when it may be your AC.

To determine if your AC is the problem, take the following steps:

  1. Make sure that you are running your AC and not your heat. The AC will not be your water source if you have not recently cooled your home. If this is the case, then you should call a professional to diagnose your system.
  2. If you have or are using your AC, look at the condensate line and drain pan to try and find the source of the leak.
  3. Once you have located the leak, contact an HVAC professional to fix the leak.

Still not sure why your furnace is leaking water? Call an Action Air tech!

We are happy to help those living in our service area with any AC or heating system issues.

Just schedule an appointment online and we will send one of our knowledgeable technicians to help diagnose and fix your furnace.