Why Is My Furnace Leaking Water?

If you're walking by your furnace and surprised by the unwelcome sensation of a squishy, wet sock, chances are good that your unit has a leak. While it may seem unusual to have a furnace leaking water, the issue is actually quite common, especially with high-efficiency models.

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From clogged drain hoses to malfunctioning humidifiers, there are many factors that can lead to water leaking around your furnace. But don't panic, as most issues can be remedied with the help of a professional HVAC technician.

Why Is Water Dripping From My Furnace?

Issues with the condensate pump, drain hose or drain line are some of the most common causes of leaks in high-efficiency furnaces. If you have a conventional furnace, there may be a problem with a shared or nearby humidifier, or the exhaust pipe might be improperly installed. Here's a deeper look into the possible causes of a leaking furnace:

• Clogged condensate drain hose: If the condensate drain hose that connects to the exhaust pipe on your high-efficiency furnace becomes clogged, this can lead to water leaks around the furnace. Leaks can also occur if the hose is disconnected or damaged in any way.

• Malfunctioning condensate pump: A malfunctioning condensate pump can prevent the condensate in your high-efficiency furnace from draining properly. This may lead to water backups and pools of water around your furnace, and you may also notice rust or water spots on the inside of the furnace cabinet. `

• Clogged condensate trap: If your high-efficiency furnace has a built-in condensate trap, water leakage may occur if the trap becomes clogged. Clogs and blockages can sometimes lead to condensation backing up and overflowing, resulting in water pooling around your furnace.

• Damaged inducer assembly: The inducer assembly on high-efficiency furnaces serves as the area where condensation flows from the exhaust pipe and into the condensate drain hose. Cracks and other types of damage can cause your furnace to start leaking water.

• Malfunctioning dehumidifier or humidifier: If your whole-house humidifier attaches to your furnace or if your furnace and dehumidifier use a common drain, malfunctioning of either unit can cause water to pool around the furnace. With humidifiers, cracks and damaged components are the most common causes of water leaks, and dehumidifier leaks are usually due to overflows or clogs.

• Loose exhaust pipe: If the exhaust pipe on your furnace is loose, improperly installed or damaged in any way, this can cause the condensate that should be released through the pipe to build up and leak on the floor.

• Blocked air return or clogged air filter: Blockages within your furnace's air return can hinder outgoing airflow. When this happens, condensation may build up inside the furnace air handler and eventually leak out and around the furnace housing. Clogged or dirty air filters can also lead to inefficient air flow and condensation buildup.

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Is a Furnace Leaking Water an Emergency?

In general, a furnace leaking water isn't considered an emergency. However, it can be potentially dangerous if your furnace or the pooling water is in close proximity to other electrical appliances or components. Excess water buildup can also lead to water damage to both your furnace and the underlying flooring. To be safe and prevent as much damage as possible, it's best to turn your furnace off quickly and schedule a professional service call if you notice water leaking around the unit.

What Should You Do if There's Water Coming From Your Furnace?

If your furnace is leaking water, the first thing to do is shut the furnace off and contact a professional HVAC company to schedule a service call. Next, use a dry towel or wet/dry vac to soak up the water surrounding the unit to reduce the risk of water damage. Once your HVAC technician arrives, they'll perform a detailed inspection of your furnace and accurately diagnose the issue.

If your furnace leak is due to a clogged air filter or condensate drain, these problems can usually be fixed by replacing the filters and clearing the clogged drain or drain hose. If the issue lies within the condensate pump, it may require repair or replacement. Condensate pumps generally last three to five years before they start to malfunction. In some cases, your HVAC technician may need to replace or repair the connected or built-in humidifier to get things running smoothly again.