Why Is My Furnace Leaking Water? How To Fix It [With Pictures] (2024)

Water damage is one of the most common household disasters. A water leak can be a major headache and even cause bio-growth to grow. This will make you sick and cost a lot of money to repair.

However, we've all been there, as a furnace leaking water is a common problem for homeowners to deal with. A water leak from your furnace could lead to high repair costs; and even worse, if it does produce bio growth, this could damage your property and pose a severe risk to your health. If it continues to leak, your furnace will eventually fail and need to be replaced.

It's always better to address a water leak early before it becomes a problem. An unchecked furnace leak can lead to more costly repairs down the road, so homeowners should never overlook it. This post provides information on why furnaces leak water and what can be done about it! Call now so that we can stop the problem before it becomes bigger issue.

schedule service

How Does My Gas Furnace Work And Does it Produce Water?

For starters, lets dig into how your furnace works. When the indoor temperature dips below the thermostat's set temperature, the thermostat sends a signal to the control board inside the furnace to begin the heating cycle. This starts by turning on an ignition switch, opening the gas valve, and turning on the draft fan to create combustion. The combustion warms the heat exchanger. The flue gases inside the heat exchanger are released outside through the exhaust pipe. After this, the blower fan blows cool air from inside your home past the heat exchanger. This is where the air absorbs the heat and is then forced through your house's ventilation system to heat the house. That's how warm air is made!

Additionally, if your furnace is struggling to turn on at the start of the cold season, consult our blog to learn more!

Got the basics? So where does the water come in?

A conventional furnace, also known as a standard efficiency furnace, does not produce water. However, if you have a high efficiency furnace, (90% efficiency), condensation will arise due to the addition of the second heat exchanger. This is why a high efficiency furnace is also known as a condensing furnace, and a standard efficiency furnace is a non-condensing furnace.

Primary Heat Exchanger

What kind of furnace unit do I have?

Now, let's figure out the type of furnace you have.

It is relatively easy to identify your furnace type and narrow down the reason for its leak. Look at the exhaust pipe. If it is white plastic furnace PVC pipe, then it is a condensing furnace, making it high efficiency. A metal exhaust pipe has a standard efficiency rating and does not produce condensation.

When a high efficiency furnace releases the exhaust gases, condensation is created. This condensation is a significant amount of moisture on the PVC pipe and needs to be drained into either a floor drain or a condensation pump. A water leakage occurs when the condensation is unable to drain properly.

Let's provide some examples:

Leaking From Condensate Drain Hose

The drain hose, which slopes down from the PVC exhaust pipe, can easily become clogged with debris, dirt, and dust. If any tubing that aids the draining is damaged, disconnected, or clogged, this is when a condensation leak occurs.

Condensate Drain Hose

Inducer Assembly Leaking

Next, the condensation runs down the exhaust / flue pipe, through the condensate drain hose, and into the inducer assembly. If the inducer assembly is cracked, water can leak out of the furnace.

Leaking From Condensate Drain Line

As the water exits, it passes through a condensate drain line. If this has a loose connection, cracks, or holes, it can cause water leakage. Also, if the drain line is clogged, it can cause the condensate to back up and create a water leak.

Leaking Out Of The Condensate Trap

A clogged condensate trap can cause condensate to back up and overflow out of the furnace. Note, not all high-efficiency furnaces have a condensate trap.

Condensate Pump Leaking

The condensate pump is where the condensate eventually drains into. This is yet another component that can clog and lead to a leak. A blocked drain, or even a partially blocked drain, will result in the furnace leaking. If you notice water on the floor around your high efficiency furnace unit, or water or rust stains within the cabinet, your furnace is not draining properly. Similarly, a malfunctioning pump can cause water to back up and create a furnace leak. In this situation, a professional will have to replace it. Most condensate pumps last 3-5 years; after that, they tend to not perform as optimally.

Overflowing condensate pump

Why is Non-High Efficiency Furnace Leaking Water?

If your furnace unit is a conventional furnace operating at standard efficiency, then it will not generate any water. If there is standing water around your furnace, it is probably coming from another appliance.

Here are a few appliances to look out for:

Water Leaking From Air Conditioner

When your AC unit is running, it generates water, making it a common source of leaks. Your AC may leak for a number of reasons, such as:

Damaged Drain Pan

All AC units have a primary drain pan located under the evaporator coil. Some AC units also have a secondary drain pan beneath the unit. The purpose of the drain pan is to catch any condensate. If there is a crack or hole, the excess water will spill or leak out.

Water leak from attic drain pan

A Frozen Coil

If your evaporator coil freezes, your AC unit will leak.

Frozen Evaporator Coil

Clogged Drain Line

A clogged drain line will cause the drain to disconnect from the drain pan if water cannot pass through. The water will then drip and pool around your AC.

Failed Condensate Pump

A condensate pump is necessary to drain the condensation from the HVAC. If you have a high-efficiency furnace, the furnace and air conditioner most likely share the condensate pump.

Learn more in ourAC leaking water blog!

Water leaking From Hot Water Heater

Cleaning up a furnace leaking water. Rust has formed from the water leaking.

rusted and cracked heat exchanger

Rust on furnace control board

furnace leaking water on control board

What Should I do If I Have A furnace leaking water

Furnace switch

Cleaning up a furnace leaking water

Remove furnace door

Take control of your home comfort

with A superTech Furnace Repair

schedule service

How can I prevent my furnace From leaking water in the future?

If you have a leaky furnace, it’s important to get the problem fixed as soon as possible. The longer your heating unit is leaking water and losing energy efficiency in the winter, the more likely it will be for you to experience other problems with your home or property. So, if you find that your furnace is leaking water or not heating your home, don’t hesitate to call Baltimore's best furnace repair company. Don't let another day go by without getting that pesky leak taken care of. Every minute wasted only makes things worse when it comes time for a furnace repair. Schedule online or call our experts today so we can repair your leaky furnace before anything else goes wrong!

Contact us today if you have questions about a leaky furnace—or if you simply want more information about how to keep your home safe and healthy. We offer furnace repair,furnace maintenance, and newfurnace installation.