Finding water leaking in your furnace can be concerning, especially during the winter months when you rely on it most. Furnace leaks are a fairly common problem, and it’s important to address them quickly to prevent further damage to your home.
While the obvious assumption might be that the furnace itself is failing, the truth is that the source of the water could be coming from a number of different places. It could even be a sign of something unrelated to the furnace, like a roof leak.
This guide will help homeowners understand why their furnace might be leaking, how to troubleshoot the problem, and when it’s time to call in a professional for help.
Is it really the furnace? Finding the source of the leak
Before you assume the furnace is the culprit, take a look around and see if you can rule out other appliances in the area. It’s possible the water is coming from somewhere else.
Ruling out other appliances
Start with a basic process of elimination to rule out the usual suspects: the water heater, water softener, iron filter, and dehumidifier. It’s not uncommon for older furnaces to be located near other appliances that could be the source of the leak.
Humidifiers, for example, can leak if the pad needs replacing, the drain tube is clogged, or the filter isn’t installed correctly.
Winter leak or summer leak?
When the leak occurs may give you a clue as to the source. If the leak only occurs in the summer, that may rule out the furnace itself. Instead, check the air conditioner drain lines, the evaporator coil pan, or the coil itself. Any of these could be blocked or leaking.
Common Causes of Furnace Leaks
If you see water around your furnace, it’s important to figure out where it’s coming from and fix it.
Condensate Drain Line Issues
Newer, high-efficiency furnaces often have a condensate drain line and inducer assembly. The condensate drain line removes water that’s created as the furnace heats your home. If that drain line gets clogged or blocked, it can leak.
The best way to prevent clogs and other problems is to have your furnace tuned up every year. If you suspect a blockage, try disconnecting the drain hose and flushing it out.
Condensate Trap Problems
Another potential culprit is the condensate trap. This trap, like the drain line, can become clogged. If you suspect the condensate trap is the source of the leak, it’s probably best to call in a professional.
Condensation Pump Malfunctions
Some furnaces use a condensation pump to remove water. These pumps can fail or leak, and they usually last only 3 to 6 years.
Ventilation and Exhaust Issues
Your furnace relies on a system of vent and intake pipes to function properly. The intake pipe brings in fresh air to fuel the combustion process, and the vent pipe expels the resulting exhaust gases safely outside your home.
Vent and Intake Pipe Problems
If these pipes develop cracks or splits, or if they become blocked by debris, several problems can arise, including water leaks. Here’s why:
- Compromised pipes can allow rainwater or snow to enter the furnace system directly.
- Cracks or blockages can disrupt the proper flow of exhaust gases, leading to condensation within the furnace.
Addressing External Water Intrusion
If you notice a leak occurring during or after a rain or snowstorm, there’s a good chance the water is entering through the vent or intake pipes. Here’s what you can do:
- Carefully inspect the pipes for any visible damage, such as cracks or splits.
- Clear away any snow, ice, leaves, or other debris that may be blocking the pipes.
Internal furnace component leaks
Sometimes the water isn’t coming from a drain or condensation line. It’s coming from inside your furnace.
Heat exchanger leaks
The heat exchanger is a critical part of your furnace that warms the air blown through your vents. It works by separating the extremely hot combustion gases from the air you breathe. If the heat exchanger is cracked or corroded, dangerous gases like carbon monoxide can leak into your home. For that reason, it’s important to have a professional HVAC technician diagnose and repair any problems with your heat exchanger.
Inducer motor issues
The inducer motor is a fan that helps vent combustion gases from your furnace. If the inducer motor isn’t working correctly, it can cause water to leak from the furnace. Sometimes the motor housing itself can crack or corrode, which can also lead to leaks.
As with a faulty heat exchanger, inducer motor issues require a professional to diagnose and repair.
Other Potential Leak Sources and Contributing Factors
Sometimes, the water around your furnace isn’t actually a furnace leak at all.
Humidifier Leaks
Many homeowners have a humidifier attached to their furnace. A broken humidifier can drip, and you might think the water is coming from the furnace. If the humidifier is leaking, try replacing the pad, flushing the drain tube, and checking to make sure the filter is installed correctly.
Dirty Furnace Filter
A dirty furnace filter restricts airflow. This can cause the furnace to work harder, which may lead to condensation and, potentially, a leak.
Faulty Condensate Pump
Finally, if your furnace has a condensate pump, a leak could be coming from the pump instead of the furnace itself.
Final Thoughts
If you notice water leaking from your furnace, your first priority should be safety. Turn off the thermostat and the furnace’s power switch immediately.
Regular furnace maintenance and inspections can help prevent leaks and other problems. If you haven’t scheduled a furnace checkup recently, now’s a good time to do it.
While you might be able to address some minor issues yourself, like clearing snow from intake pipes, many furnace repairs require a professional. If you suspect a heat exchanger leak or are dealing with any electrical problems, don’t hesitate to call a qualified HVAC technician. You should also seek professional help if you’re uncomfortable with any aspect of the repair.
Taking proactive steps to prevent and address furnace leaks can save you money, improve your home’s energy efficiency, and, most importantly, keep you and your family safe.