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Furnace Leaking Water When AC Is On: Causes And Solutions

Don’t hesitate to contact Carrano Air if you notice furnace leak from your unit or air conditioner. Request an appointment with our team today.

As summer approaches and temperatures rise, you need air conditioning in your home to keep the interior cool and comfortable. The last thing you expect is your furnace leaking water when the air conditioning is on, but this happens more often than you think. Although common, a leaky furnace can cause major problems with your HVAC system, your home’s energy efficiency, and your safety.

As a furnace replacement and installation professional in South Brunswick, Carrano Air HVAC Contractors Inc. is committed to providing the best HVAC repair services to all of our customers. Our NATE certified team understands the dangers of a leaky furnace. Here we will explain how this situation occurs most often and what you can do to avoid it. 

Possible Reasons for Furnace Leak

It can be assumed that a water leak in a furnace when the air conditioning is switched on indicates a problem with the heating system. However, the problem affects one or more components of your home’s central air conditioning system.

Air conditioning units produce condensation due to their operation. As the unit’s fan draws in warm air from inside your home, it flows over the system’s evaporator coil, which contains refrigerant. As the refrigerant absorbs heat and moisture from the air, condensation forms.

The condensate drips from the coil into a drain pan before draining out the condensate line, where it drains out of your home. Although a central air conditioner often produces moisture during operation, it should not produce excess water that could leak from your furnace. If your furnace is leaking indoors in the summer, it may be due to one of the following problems. 

1. Clogged Condensate Drain Line

A condensate drain line is a sturdy metal or plastic pipe that an HVAC contractor connects to a central air conditioning system. The pipe acts like a funnel that leads outside. When an air conditioner creates condensation by producing cool air and reducing humidity in a building, moisture collects in the exhaust duct and flows outside.

As air flows through the refrigeration system and over the evaporator coil, airborne contaminants such as dust and dirt also accumulate in the moisture produced by the coil and refrigerant thanks to heat transfer. Over time, debris builds up in the condensate drain line, causing blockages that can prevent water from properly draining to the outside.

If your system has a clogged drain line, water is likely collecting at the base of your HVAC unit. Removing dirt, mud, and rust from the condensate drain line should be part of your air conditioning system’s regular maintenance to reduce the risk of developing this problem.

2. Disconnected Drain Line

Your air conditioner’s condensate drain should not be interrupted for any reason. However, it could come loose if someone comes across it after working on or near the cooling system. A loose condensate line could also indicate poor air conditioning installation.

If you suspect there is an AC leak in your furnace, check the line to make sure it is still connected to the system outlet. Tighten the line and ensure a proper seal if necessary.

3. Clogged Air Filter

Debris from a clogged air filter can also cause a furnace water leak when your air conditioner is on. The air circulating through an HVAC system passes through a filter to capture suspended particles, creating cleaner, fresher indoor air. However, you should change the filter regularly to prevent the screens from becoming clogged with dirt, hair, pollen, dust mites and other pollutants.

Dirty air filters can cause the evaporator coil to freeze. If enough air cannot circulate through the piping to facilitate heat transfer, the coil will freeze. The ice melts every time the air conditioner is turned off, causing water to leak from the furnace.

Ideally, homeowners should change filters at least every three months. If you have pets, allergies, or a dust problem, it’s best to replace your air filters once a month to prevent premature clogging.

4. Dirty Condensate Pump

A condensate pump collects and distributes the water created by condensation from the heating and cooling system. You will likely need this air conditioning component if the system does not use gravity to drain water from the condensate pan to the drain line. Without a pump or gravity drainage system, water will continue to collect in the container, overflow the sides, and form puddles on your floor.

If your system has a drain above the device, make sure the pump is clean and free of debris. A plug prevents the condensate pump from pumping water out of the tub. But even if it’s clean, a faulty pump can cause the same problem.

5. Faulty Evaporator Coil

Sometimes the problem with a leaking furnace or air conditioner is a faulty evaporator coil. If the pipe has a crack or other damage that prevents it from functioning properly, the condensation could splash out instead of flowing directly into the drain pan.

Not only would moisture seep into your floor and walls, but it would also drip onto the air conditioner’s electrical components. Water near electrical components poses a serious electrical fire hazard. If you suspect that your refrigerator’s evaporator coil is defective, you should take immediate action and contact a qualified HVAC professional.

Your evaporator coil may be broken if you notice these signs in addition to an HVAC leak:

  • Your AC unit will not turn on 
  • The air coming from your vents is warm
  • Refrigerant is leaking from the indoor portion of the cooling system
  • The air conditioner stops and starts often without cooling your home efficiently

6. Cracked Drain Pan

A dirty water tank must be emptied regularly to avoid leakage due to overflow. Like other HVAC components, the tub could be faulty or damaged, resulting in reduced performance. For example, a cracked drain pan will cause water to drip out of the hole and wet the inside of your air conditioner.

You might initially overlook a damaged paper bin. However, water that leaks from the pan will eventually enter the HVAC unit and cause a visible puddle or water damage around your furnace. Fortunately, fixing this problem is as easy as replacing the cracked condensate drain pan.

Is It Bad for a Furnace To Leak When the AC Is On?

If your furnace is leaking water while the air conditioning is on, you could be facing serious long-term problems if you don’t take immediate action. Moisture damage is one of the biggest problems you can face if a furnace starts leaking.

Even if your furnace doesn’t appear to be leaking excess water, it could still result in thousands of dollars in property damage if you don’t correct the situation. By fixing the leak as soon as you discover it, you can prevent significant damage to your home’s flooring, framing, and walls. Excessive humidity can also lead to mold growth in your home and allergy problems such as:

  • Wheezing
  • Stuffy nose
  • Itchy skin
  • Red eyes
  • Asthma triggers
  • Coughing

If property damage or mold problems are not addressed, it can pose serious risks to your home and impact its value and safety. It can also lead to costly repairs to the home and HVAC system.

It’s always best to fix heating and cooling leaks as soon as you notice them. The longer you ignore a leak, the more expensive the damage will be to repair.. 

How To Stop Furnace Leaks When Your AC Runs

Repairing a leaky furnace requires much more than just cleaning up water spills. You must also determine the cause of the leak and make necessary repairs (or replacement) of the faulty parts. Follow these steps if you notice water leaking from your furnace while your air conditioner is running:

  • Shut off the AC: Turn your HVAC unit off before you even touch it. To ensure proper safety, you can shut everything down from your home’s fuse box. 
  • Clean up: Promptly clean any mess the leak creates. The longer you ignore standing water, the bigger the risk of inflicting extensive property damage. 
  • Check the air filter: Inspect the air filter to ensure it’s clean or replace it if dirty. Use a water-safe vacuum to remove debris from the unit. 
  • Turn on the AC: Turn the cooling unit back on after cleaning it. If the leak stops, you’ve fixed the problem, but you should contact an HVAC contractor if the problem continues.

Call Carrano Air To Keep Your AC and Furnace Leak-free

No HVAC project is too difficult for the technicians at Carrano Air HVAC Contractors Inc. From variable speed furnace installation to quality air conditioning maintenance, our HVAC experts can handle it all. Our trusted heating and cooling team in South Brunswick, NJ leverages the best products and years of industry experience to provide the best possible service with a 100% satisfaction guarantee.

Stop a furnace from leaking water when your air conditioner is on with Carrano Air HVAC Contractors Inc. Call our team at (732) 329-3784 to request a quote.

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