Why Is My Air Conditioner Leaking Water? 7 Causes (and How to Fix It)

Find out why your AC unit is leaking and how to resolve this problem.

An air conditioner helps keep a home cool when the temperature outside begins to soar. This appliance pulls warm air over cold evaporator coils to cool the air before carrying the cool air back into the home. It also releases the collected heat to the outdoors. Without a working air conditioner, a home can get uncomfortable in a hurry, so it's important to take action as soon as you notice something wrong with the appliance.

One common problem with air conditioners is that they may start to leak water. If you notice this, the first thing you need to do is turn the air conditioner off. In some cases, this should stop the leak, but if the leak is due to frozen evaporator coils, it could take 30 minutes to an hour for the coils to fully thaw. Grab a shop vacuum and some towels to clean up any water on the ground, then prepare to inspect the appliance. Use this guide to discover 7 causes for a leaking air conditioner and how to fix it.

Related: For Heating and Cooling Problems, These Are the Best HVAC Companies to Call

How Does Water Form in an Air Conditioner?

Most air conditioners, with the exception of evaporative coolers, do not use water in normal operation, so it might be confusing when you discover that the appliance is leaking water. The water in an air conditioner forms when warm air passes over the cold evaporator coils. Cold air cannot carry as much water, so when the air is rapidly cooled, the water is squeezed out in the form of condensation.

As long as the air conditioner and all of the component parts are functioning properly, the condensation doesn't pose a problem. It drips into a drain pan, which connects to the condensate drainage line, allowing the collected water to flow into the main drain line for the home. However, if there is an issue with the air conditioner, this water may leak out of the unit.

Common Causes of an Air Conditioner Leaking Water

1. Dirty Air Filter

One of the easiest problems to fix is a dirty air filter. When the air filter is clogged, it partially impedes the flow of air into the air conditioner, making it more difficult for the unit to cool the home. The longer the air conditioner is operating, the higher the chance that the evaporator coils will freeze. When the coils freeze, ice builds up on the outside of the coils, which doesn't cause an issue until the air conditioner is off for several minutes.

During this period, the warmer air thaws the ice, causing it to melt into water. The meltwater quickly fills up the small drain pan faster than the water can drain away, leading to the air conditioner leaking water all over the floor. To fix this problem, simply change the air filter on a regular basis.

2. Wrecked Insulation

In order to help prevent condensation from forming on other parts of the air conditioner, the lines running from the outdoor condenser unit to the indoor air conditioner are insulated. However, when the insulation is cut, torn, stripped, or otherwise wrecked, it cannot properly prevent condensation from forming.

Depending on where this occurs, it may simply drip outside, or it may run into the home, causing an active leak. This issue can be resolved by replacing the damaged air conditioner insulation. Typically, you can purchase insulation online or at a local home improvement store.

3. Frozen Evaporator Coils

The purpose of evaporator coils is to cool the incoming warm air. This means that the evaporator coils must be cold to reduce the temperature of the air as it flows over the coils. When this occurs, the excess moisture in the air is left behind, clinging to the coil as condensation. Ideally, the condensation drips down into the drain pan and drains through the condensate drain line.

However, if the air conditioner has been operating for a long period of time, ice can begin to form on the evaporator coils. The longer the air conditioner works, the higher the chance that the evaporator coils will freeze. When the air conditioner shuts off, the warm air thaws the ice. The meltwater quickly overflows the drain pan, leading to a leak.

This issue is often caused by a dirty air filter, though it can also be due to items blocking the airflow around the air conditioner unit, or the temperature being set too low on the thermostat. Resolve the problem by changing the air filter, removing any obstructions, and raising the temperature to a more reasonable setting.

4. Leaking Drain Pan

When condensation forms, it drops down into the drain pan. However, if the drain pan is cracked, badly rusted, or otherwise damaged, the collected condensation may leak out of the drain pan and onto the floor. The only option to fix this leak is to replace the drain pan. DIYers with HVAC experience may be able to complete this repair on their own, but less experienced individuals may be better off calling in an HVAC repair professional.

Similarly, if the drain pan was not installed properly or reinstalled properly after a repair, it could be sitting on a slant that causes the water to collect in the corner, instead of emptying into the condensate drain line. As the water continues to collect, it will overflow the drain pan. If this is the case, it's recommended to contact the installer or another HVAC repair professional to level the unit.

Related: How Long Does an Air Conditioner Last? Tips to Extend Its Lifespan

5. Clogged Condensate Line

Another issue that can occur is that the condensate drain line may become clogged with dust, dirt, or other debris. If the drain line is clogged, then when the condensation collects in the drain pan, it has nowhere to empty into, leading to the drain pan overflowing.

The condensate drain line can usually be cleared with a mild solution of water and vinegar. The vinegar will break up any mineral deposits, dirt, or grime, allowing water to flow into the drain. However, if this doesn't work, then you may need to use a shop vac to suction out the clog. As a last resort, you can replace the condensate drain line.

6. Refrigerant Leak

Air conditioners require refrigerant to cool the evaporator coils and, in turn, cool the incoming air. If there is a leak in the refrigerant line or any components that house the refrigerant, you may notice hissing or bubbling noises from the unit. Similarly, the leaking refrigerant can cause ice to build up on the coils, leading to the appliance leaking water.

If you suspect that there is a refrigerant leak, do not attempt to fix the issue on your own. Refrigerant leaks can be very dangerous, so it's recommended to call a trained HVAC repair professional to assess the situation, repair the air conditioner, and recharge the refrigerant.

7. Damaged Condenser Unit

The condenser unit is the part of the air conditioner that sits outside the home. Despite what many people believe, the condenser does not pull air in from outdoors. Instead, this part of the air conditioner releases the collected heat outside the home, helping to reduce the overall amount of heat inside the home. If there is a crack in the condenser housing, a damaged gasket, or a refrigerant leak, it can cause the air conditioner to leak water.

It's recommended to contact an HVAC repair professional to assess the damage and suggest next steps. In some cases, the issue can be resolved with a minor repair, like replacing the damaged gasket, but in more serious situations the entire condenser unit may need to be replaced.

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