Furnace Leaking Water When Heat Is On? (Possible Causes & Fixes)

Furnace Leaking Water When Heat is On

Depending on what climate you live in, having a furnace can be an essential appliance. Especially in frigid climates, that furnace can mean the difference between comfort and freezing conditions in your own home.

Believe it or not, you may notice leaking coming from your furnace even when the heat is on. This is a fairly common problem and one that can be remedied relatively easily. It could be a plumbing leak, condenser leak, humidifier leak, or a variety of other problems. It is always a good idea to have a technician come out to inspect the problem.

Handle the Problem Immediately

Before we get into the reasons that your furnace is leaking water, it is important to note one thing. No matter what the cause of the issue, it is imperative that you resolve it in short order. And that is because water damage is nothing to mess with.

Water can permeate the tough to reach areas of your home and cause some serious issues. That can include the walls, ceiling, and flooring as well. There is also the potential that it could lead to mold growth, which is dangerous for your respiratory system over the long run.

Is a Furnace Leaking Water Dangerous?

It all depends on the situation. There are times where that leaking water can be an emergency. If you’re concerned for your safety or the condition of your furnace, shut the entire unit down before you attempt a fix or call in a technician.

More often than not, a leaking furnace is not an emergency but, as mentioned above, it is definitely not something to ignore. More often than not, proper maintenance can be enough to keep leaks at bay and preserve the condition of your furnace.

Condensation Leak

Perhaps the most common reason for a furnace leak is a condensation leak. Most furnaces are running at high efficiency. That means that the AFUE rating is at least 90 and is generally above that. Not only that, but this is the kind of furnace that has a pair of heat exchanges to let it produce a lot more heat than normal.

Condensation can be produced by that heat production getting carried out through the pipes in your home. Typically speaking, this will happen through a floor drain. When the pipes are either clogged or broken, you will notice leaking condensation near the base of the furnace. And when that water starts to build and pool up, you are looking at the potential for water damage.

Plumbing Leak

While it is entirely possible that the leaking is due to an issue within your furnace, that isn’t always the case. Sometimes, it can be as simple as an issue with the plumbing instead of the furnace. And while it’s a relief that the furnace is not at fault, that means that you now have a plumbing issue instead.

  1. Don’t wait. Any issue that can lead to water damage needs to be addressed immediately. Don’t wait or you could be staring down the barrel of even more costly repairs.
  2. Clogged or broken pipes. When there is a plumbing issue, it tends to revolve around pipes that have become clogged or broken. With these issues, water will begin to back up in your drainage system and can make it appear as if the furnace has sprung a leak. Those pipes will need to be repaired or replaced entirely.

Clogged Filter

One of the most consistent issues in a home’s furnace is the filter. When the filter gets clogged or becomes excessively dirty, the airflow can become restricted when passing through the furnace coil. Most of the time, this can cause the coil to freeze in the more inclement weather.

In other instances, though, it can cause water to start leaking, eventually pooling up around the base of the furnace. Performing routine maintenance involves checking and potentially cleaning the filter. If it is too dirty, just replace the entire thing to be safe.

Heat Exchanger Issue

Another fairly common issue with leaking in your furnace involves the heat exchanger. When the exchanger becomes excessively damaged or broken entirely, you may notice water leaking from the furnace.

The unfortunate thing is that the heat exchanger is one of the more expensive components of your furnace to fix. Should you determine that the heat exchange needs to be replaced, calling a technician is the best bet. This can be a tricky fix and you may wind up spending far more time than necessary to implement a fix if you manage to do so at all.

Air Conditioner Leak

There are some climates where using your furnace and air conditioner in the same season is not out of the norm. When that is the case, it could actually be the air conditioner that is causing the leaking and not the furnace.

This happens when the air conditioner is being used and the condensation pan fills over the top, dripping or flowing out onto the heating system. So, it may appear that the furnace is at fault, but it is really the air conditioner. Simply empty the pan and replace it to alleviate the issue.

Humidifier Leak

Another potential culprit in your furnace leaking could have to do with a clog or break in the humidifier. The humidifier helps to regulate the humidity in the air automatically.  Generally speaking, the humidifier will be hooked up to the plumbing system so that it can add any moisture in the air where necessary.

When there is a breakage in the connections or tubes, or when there is a clog, water can start to drip around the furnace. The simple solution is to check the continuity of the hose and replace it if you notice any breaks, cracks, or excessive wearing.

What Do You Do When Noticing a Furnace Leak?

Knowing what to look for is important but it can be even more essential to know how to act. As mentioned previously, dripping or leaking water can be a major nuisance and you need to act quickly to prevent major damage.

That said, there are a few important things to do before calling in a professional technician to find and repair the issue.

  1. Turn off the furnace. If the problem is actually within your furnace and not in the surrounding plumbing, the first thing to do is turn off the furnace. Letting it run will usually just exacerbate the problem and keep the leak going. The best thing to do is to locate the breaker for your furnace and shut it off from there.
  2. Soak up the water. Before moving on to anything else, you will need to remove any existing water. If it is just a little, you might be okay letting it go but be safe and remove the water. With larger puddles especially, it can leak into the flooring and cause major damage. Don’t risk ruining your floors or walls by letting puddled water persist.
  3. Check the air filter. As mentioned previously, the filter is generally a common culprit behind issues with your furnace. Make sure that it isn’t excessively clogged or dirty. If it is, buy a new one and install it.
  4. Call in the pros. You might be able to identify where the problem is. Even if you can, implementing a fix can be tough. Call your local professional and provide any information that you can to help expedite the fix.

Another Type of Leak: Carbon Monoxide

Water can be enough to deal with. There is another type of leaking, however, that can be far more dangerous: carbon monoxide. There are a few signs that you can refer to in order to determine whether or not you have a carbon monoxide leak on your hands.

  1. Heavy condensation on nearby windows. This can be an indication that your humidifier is set very high and needs to be changed. You’ll notice heavy condensation and even dripping on windows nearby.
  2. Stains. Brown/yellow or sooty stains will be around the furnace.
  3. Stale or stuffy air. You may even notice that the air smells like it has been burning. Any of these are worth having a professional come out to check the issue.

Ryan Womeldorf

Ryan Womeldorf has more than a decade of experience writing. He loves to blog about construction, plumbing, and other home topics. Ryan also loves hockey and a lifelong Buffalo sports fan.

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