Why is My Furnace Leaking Water?

My AC is Working, but my Furnace is Leaking Water

If you’ve noticed water pooling around your furnace, you’re not alone. This common issue can cause anxiety for any homeowner. While there are a multitude of causes for water leakage, we will explore some of the most common culprits and provide practical solutions to help you address the problem. By understanding these causes and taking preventative measures, you can keep your furnace running smoothly and keep your AC sharp in the St. Louis summer.

How Does My Furnace Affect My AC?

Your furnace is leaking water, but summer and your a/c is running not your furnace. Your furnace works whenever ANY part of your HVAC is running, which for most St. Louisans is year round. In simple terms, your outside AC uses refrigerant to condense air into a cool liquid, releasing heat from that air outside. The condensed refrigerant then travels to your furnace where cold air flows through the evaporator coil and the blower forces air through your ductwork and into the rooms of your home.

The Main Culprit of Water Leakage is Usually a Frozen Evaporator Coil
The evaporator coil is the most likely culprit for your leaky furnace. As the condensed air is pumped through your evaporator coil, it can freeze up. When the coil thaws, water from the thawing leaks out of your furnace.

What Happens if My Condenser Coil Freezes?

If you let this problem persist, it could become a costly issue for you down the road or even in the near future. The water leaking from a thawed condenser coil can cause internal components of your system to rust. In some cases, the leaking water can damage the control board or other vital components. If you let this problem go without addressing it, you could find yourself facing breakdowns, costly repairs, or a replacement unit in the future.

Possible Causes of a Frozen Evaporator Coil

Have You Checked Your Filter Lately?
A dirty filter is the cause of many HVAC issues and is the easiest problem to address. We recommend checking your filter monthly to make sure that it is clean. If you have a dirty filter, simply replace it (properly) and check again next month. In the case of a leaky furnace, a dirty filter is the most common cause and the easiest cause to address.

Low Refrigerant Charge

The most typical cause of a frozen coil is low refrigerant. Refrigerant is highly pressurized, so low levels of refrigerant can create a decreased pressure environment for the coil. This means the remaining refrigerant will expand and cool rapidly, causing the coil to freeze. If you see ice when you open the front panel on your furnace or on your black refrigerant lines that go from your air conditioner outside to the inside of your home, you have a refrigerant problem and need service. This ice will not look clear, it will appear white.

Refrigerant Charges – DO NOT TRY THIS AT HOME!

Attempting to replace refrigerant is not a DIY project. You need a qualified HVAC professional to perform this task for your safety and the safety of your HVAC system. Call us at 314-819-0028, or schedule service to have one of our experienced technicians check your refrigerant charge.

Other Possible Causes and What You Can Do

The Problem- Insulation Sucked Into Evaporator Coil
The adhesive holding the internal insulation to the walls of your furnace could be degrading. When that happens, the insulation can get sucked against the side of your coil, restricting the air flow and causing the coil to freeze up.

What Can I Do?

Contact us. You’ll need specialized expertise to fix the issue, which isn’t readily apparent without the blower motor running.

The Problem- Closed Return Grills/Registers

If you have a lot of air vents closed, or covered with furniture, rugs, etc., you could be disrupting the air flow in your HVAC system. Restricting airflow can create a pressure imbalance.

What Can I Do?

Take a walk around your house. Identify where your vents are in each room and make sure the registers are open and/or uncovered.

The Problem – Blower Not Running Correct Cubic Feet per Minute (CFM)

Your blower fan could be causing airflow issues and leading to your frozen coil. If this is the case, you may notice unusual noises or weak airflow.

What Can I Do?

This is another problem that calls for a professional. One of our technicians can check your system and diagnose any issues your blower fan or other components may have.

How to Prevent Your Furnace from Leaking Water

There are several easy steps you can take to prevent your leaky furnace:

  • Regular HVAC Maintenance
    Having your system serviced by an HVAC professional regularly can prevent a multitude of problems, including a freezing condenser coil. Members of Air Comfort Service’s Preferred Partner Plan receive two HVAC System Checks each year in which our technicians thoroughly check the components and function of your entire HVAC system. Learn more about the Preferred Partner Plan here.
  • Check Your Filter Monthly
    Make sure to check your filter monthly and if it appears dirty, swap it for a fresh filter.
  • Check Your Registers
    Take a walk around your home and check that your registers are open and unobstructed by furniture or other items.

Schedule AC Service in the St. Louis Area

If your furnace is leaking or you want to make sure your equipment is running the way it should, schedule service with Air Comfort Service today. We service the St. Louis City and County, St. Charles County, and Jefferson County areas with over 55 years of award-winning excellence.