HVAC Repair Tips


A furnace leaking water can be confusing, more so, if your furnace is heating your house fine. However, a furnace leak can also affect the heating capability of the unit so you should not ignore the problem and let a furnace repair service to inspect your furnace. Here, we will show why a furnace leaks water and how you can fix it.

Does A Furnace Produce Water?

The answer to this question depends on the type of furnace you have. There are two types of furnaces. Standard furnaces and high-efficiency furnaces. A standard furnace doesn’t produce water. They are the old type of furnaces and are also called non-condensate furnaces.

On the other hand, a high-efficiency furnace does produce water because its functioning involves condensation. They are also known as condensate furnaces or modern furnaces.

To spot which furnace you have, check out the exhaust pipe that is on the top of the furnace. A metal flue means that you have a standard furnace while a PVC pipe shows that a high-efficiency furnace is installed in your house.

Causes Of A Leaking Furnace


We explained above that high-efficiency furnaces produce condensation. So, a common reason for these furnaces leaking is the water from condensation that was not drained or exhausted. It’s usually due to a clog in the condensate drain hose, condenser drain line, condensate trap, or the condensate pump.

These parts become clogged and restrict or completely stop water from draining. As you result, you see water pooling around your furnace. Get an expert to check all the pipes and unclog them to resume the normal functioning of your furnace.

Furnace Humidifier Issue

Both types of furnaces have a humidifier that uses water from the plumbing to humidify the hot air coming from the furnace going to the vents. Commonly, the leak can be due to a loose pipe or any other problem letting water drip from the humidifier and stand near the furnace. Sometimes, the drain hose is clogged or not positioned correctly which makes the incoming water go back and cause leakage.

However, this is not uncommon as leakage can be an issue with furnace humidifiers which you can avoid or fix with regular maintenance. You should schedule maintenance once or twice a year to catch problems early on and fix them before they become a headache.

That being said, a leaking humidifier can be a health concern because if it’s leaking into your furnace, this means it’s allowing contaminated air into the furnace which is then circulated in your home. Mold and bacteria can grow in this environment and can affect various components of your central air system and your health.

Bad Vent Pipe Design

Standard furnaces have a vent pipe that flows out gasses produced during the heating process. A poorly designed vent pipe will allow air to circulate which will trap the gasses in the flue. Because of this, the gasses will cool in the vent pipe and form condensation.

Problematic Heat Exchanger

A heat exchanger is a set of coils that heat up inside a furnace. When they become hot, the blower fan works to direct the heat from the heat exchanger to the ducts and you sense warm air in your house.

Standard furnaces have only one heat exchanger while high-efficiency furnaces have two heat exchangers. The secondary heat exchanger uses the exhaust gasses to create more heat. These gasses are usually wasted if there is no secondary heat exchanger. With the additional heat, the furnace warms up the house more quickly and efficiently. That’s why they are known as high-efficiency furnaces.

However, a furnace leakage can be the result of a faulty secondary heat exchanger. When the secondary heat exchanger operates, condensation occurs due to the gasses cooling down. Because of cracks or any other reason, the condensation/moisture might leak and become visible as standing water on the floor near your furnace.

A heat exchanger is one of the costliest components of a furnace. Sometimes, a damaged heat exchanger may force you to replace the furnace. This is more likely if an old furnace.

Bear in mind that whether it’s the primary or secondary heat exchanger, a leaking heat exchanger is a dangerous issue that must be fixed as soon as possible. The burning process occurs inside the heat exchanger which is safe until the component sustains cracks or small holes. Then, it can leak harmful gasses like carbon monoxide (CO) into your house. CO is also called a silent killer because it doesn’t have any smell or color. Carbon monoxide is a toxic gas that can cause dizziness, confusion, unconsciousness, and in some cases, death.

Although you should hire an experienced HVAC contractor to inspect your furnace including the heat exchanger to look for cracks and why your furnace is leaking, if you think the heat exchanger is bad and want to check it out yourself, check out these things:

The Flame Color

Except electric furnaces, all other types of furnaces have a flame so you should see the color of the flame. A blue flame denotes that you don’t need to worry about it. But if the flame is yellow, there can be a problem. A flame becomes yellow when it’s receiving oxygen from somewhere. This is mostly due to a gas leak.

Weird Odor

A cracked or leaking heat exchanger might still create weird smells even though carbon monoxide is odorless. So, if you sense a new and strange smell in your house and it becomes stronger near the furnace, consult an expert.

Weird Sounds

Sensing weird things is how you detect problems. If you don’t sense any weird smell, try to hear any weird sound coming from the furnace. A cracked heat exchanger produces a rattling noise when the furnace cycles on and the heat exchanger heats up.

This happens because the crack will make the metal around the heat exchanger contract and expand differently than usual leading to new and strange sounds. They can be rattling, banging, or popping noises.

Carbon Monoxide In Your Indoors

As carbon monoxide is odorless and colorless, homeowners use CO detectors to identify a CO leak so they can act fast to fix the problem. As a malfunctioning or cracked heat exchanger leaks carbon monoxide into your house, you can detect it with a CO detector. So, make sure that the detector is regularly maintained so it performs its job properly.

In case your carbon monoxide detector signals CO leaks, turn off your furnace immediately, open the windows, gather everyone to an open part of your house like the backyard, and call in an expert.

The Leak Could Be From Other Parts Of Your HVAC System

Another reason your furnace has standing water around it is something wrong with other parts of your HVAC system. A clogged drain pipe of an HVAC can cause leaks and it will appear that your furnace is leaking water. Similarly, if the evaporator coils freeze up, they will melt after some time and leak water.


Furnaces usually leak water when a component is clogged, cracked, or malfunctioning. So, check the condensation pipes, furnace humidifier and its pipes, and heat exchanger. For a proper inspection, get HVAC companies Arlington involved.


Your email address will not be published. Required fields are marked *