Water Leak From Central Air Conditioner (What To Do About It)

There are two types of repairs that no homeowner wants to face. One is repairing water damage, and the other is a faulty air conditioning unit (especially in the middle of a hot summer). But when the two problems come together, the results can be significant pain. 

Several common reasons for water leaks come from your central air conditioning unit. Most of these ways are avoidable with proper maintenance of your air conditioner. The best way to stop a water leak from your air conditioner is to call a professional immediately when your air conditioner acts abnormally. 

How Do I Know If My Air Conditioning is Leaking Water?

There are many tell-tale signs you can watch for to clue you in on a leaky air conditioner. Unfortunately, these signs mean that your house will already have water damage. You must act immediately to minimize the damage if you see any of these signs.

A puddle forming somewhere in your house as water leaks down the walls is a dead giveaway that something is wrong. If the air conditioner is the source of the water, then the leak is likely to be slow-forming or is only active when your air conditioner is active. It will also put out less water in general than a burst pipe.

Leaked AirCondition

Another sign is the smell of mold or mildew throughout your house, especially when your air conditioner is running. This smell may also be present in rooms of your home with water damage on the walls.

A leaky air conditioner may also smell or feel wet when blowing. If the humidity is higher than usual when your air conditioner is active, or you notice that things tend to get a bit moist under your air vents, you may have a leak in your air conditioner.

Alternatively, the air conditioner may need to be cooling better. If you notice that your vents are not blowing cool air, it may or may not be a leak at fault, but something is wrong.

Will my A/C Still Work if Water is Leaking?

If your air conditioning unit leaks water, it will still work as if nothing is wrong. It will still come on when the temperature exceeds what you set as the desired temperature. 

However, even if you do not notice any signs of leaking water, you may see something amiss with your air conditioner. It may take longer than expected to cool the house or not cool the home. 

If your air conditioning unit is faulty, the best thing to do is to turn it off until you figure out what the problem is. This is especially true if you see signs of a leaking air conditioner.

Open Airconditon

A broken air conditioner is an inefficient one. By continuing to run your air conditioning, you are paying more for energy than you are getting in cool air.

Furthermore, continuing to run the air conditioner when a problem may strain or overheat the compressor unit or cause further issues somewhere else in your system. This will lead to even more expensive repairs. A professional can diagnose the problem quickly for you and have the air conditioner running again as it should in no time.

Reasons You Have a Leak

Unfortunately, there are several reasons you could have a leak from your air conditioner. The best way to troubleshoot it is to check the more common sources of water leaks. If you spot an issue in one area, check the other areas because the problem could have multiple sources.

Clogged Drain Line

A clogged drain line is the most common reason an air conditioner leaks water. An air conditioner also acts as a dehumidifier. While it is processing the air, it collects debris and dirt from the air. 

Drain Line of AC

If left unchecked, the debris can clog the drain line. When this happens, water will collect in your unit and eventually spill out of the drain pan. 

Some units have a sensor on the drain line that will shut the unit down if it gets blocked up. If your unit doesn’t have this, it will spill water from the drain pan into your home. 

Damaged/Rusted Drain Pan

The drain pan, too, can be a source of water leaks, especially in aging systems. Your drain pan catches condensation from your air conditioner’s evaporator coils and feeds it to the drain line. Over time, the drain pan can begin to rust or crack. 

Rusted Drain Pan

You can clean a rusted drain pan. Use sandpaper to remove the rust, then use a rust converter on the damaged areas and dry it off before replacing it.

If the drain pan is cracked, you can use water-resistant sealant to patch it up. If this doesn’t work, you can replace your drain pan. However, it has to be the right size for your make and model to work correctly. 

Broken Condensate Pump

A condensate pump helps remove water from your air conditioning system. This is especially important if the central HVAC unit itself is in a remote location in your house. As the water level rises in the pump, the float switch rises until it activates and drains the water. 

Water will accumulate if that switch (or the condensate pump in general) is broken. At some point, it will overflow and spill out. 

Condensate Pump of AC

Unfortunately, this is not a DIY problem. If you have traced a problem to the condensate pump, contact a professional to come and fix your unit.

Poor Installation

While it’s unfortunate, sometimes bad installations happen. It could be something you overlooked if you took on the HVAC installation as a DIY project or if it was a mistake by the professional you hired.

Screwing the AC
Poor Installation

In any case, poor installation can lead to several issues, such as the drain pipes needing to be in proportion with the air conditioning or the central unit needing to be level. The best solution for this problem is to call a professional to look into your system. Explain to them how the system was installed and where you believe the problem to be, and they can help you resolve the issue.

Dirty Air Filter

All the air flowing through your system must pass through the air conditioning’s air filters. This serves the purpose of straining out the dirt and particulates in the air. The process ensures dirty air is not floating around in your house.

Dirty Air Filter

An air filter will eventually get saturated and no longer work effectively. It is essential to change them out frequently (about once every three months) to ensure the air quality in your house.

A dirty air filter leads to lousy airflow. Warm air cannot pass through to be cooled, so your evaporator coils will start to freeze.

Low Refrigerant

Refrigerant is what your air conditioner uses to cool air down, similar to your car using freon. However, unlike freon, refrigerant isn’t mixed with the air and cannot ‘run low’ through use. 

Low refrigerant means that there is a hole or leak in your coils. If there is a leak, you may be able to detect it as a hissing or bubbling in your air vents.

Low Refrigerant on the AC

Working with refrigerant is hazardous, and most states require certification for handling it. So if you have a refrigerant leak, it will not be a DIY fix. Call a professional as soon as possible to repair your system.  

Broken or Frozen Coil

Evaporator coils can freeze up and cause moisture to build up. When they unfreeze, they can overflow your drain pan and leak out. 

This problem is usually paired with an airflow problem, such as dirty filters. If your coils are broken or frozen, check your filters and ducts, and return vents to see if they are dirty. 

Damaged Coil

If this does not solve the problem, another potential source for this issue can be low refrigerant, which will cause the coils to become cold. If this is the case, you will need to call a technician to fix the refrigerant before the problem is solved.

Condensation Build-Up

Condensation typically occurs as part of the HVAC’s dehumidifying system. It is drained through the drain pipe as part of the air conditioner’s normal operations. However, other things can contribute to condensation buildup and cause the air conditioner to leak water into the ducts.

AC Diagram
Image Credits: www.learnmetrics.com

If your ducts are not adequately insulated, the difference between cold air on one side and warm air on the other will cause condensation to build up in the ducts. This excess moisture can feed mold growth in your air ducts, which is hazardous to your health. 

Leaks from outside sources, such as water from a leak on your roof, can also introduce more moisture into the system, leading to condensation buildup.

Ways to Stop Leaks in the Future

It is essential to stay on top of issues that can cause air conditioner leaks because of the potential for expensive water damage. Fortunately, there are a few ways to take care of your system to prevent leaks in your house. 

Check Your Air Vents

Make it a point to check your air vents at least once every three months. Ensure that the ducts are secured and closed off, so your house has proper airflow. Open any closed vents and ensure that they are blowing air when the air conditioner is on.

It would be best if you also cleaned your air vents to eliminate any dust that might have settled on them. You can do this with a duster and a vacuum or remove the grates and give the vents a deep cleaning with soap and warm water. 

Change Your Air Filter Regularly

It would help if you changed your air filters at least once every three months. However, there are washable filters that can cut down on the expense of having to replace them. 

If you want your washable filters to work at peak performance, you will want to check your filter every month to see if a good cleaning is necessary. You can take a vacuum to your washable filter and eliminate the dust that has been caked on.  

For a deeper clean, wash or soak the filters with warm water and a little white vinegar. Let them dry, then place them back into your system.

Defrost Your Evaporator Coil

If you have been running your air conditioning hard or even suspect that your coils are frozen, it is a good idea to defrost your evaporator coils. Turn off your air conditioner and keep it off for 24 hours. This should be sufficient time for them to thaw out and for your system to return to normal.

If you are doing this during the middle of summer, you may need your air conditioning on sooner rather than later and may be tempted to avoid defrosting the coils. Don’t wait – you can use a hair dryer to assist them in thawing out. 

Hire Professional Maintenance

The best thing to do regarding your HVAC is to have a professional maintenance service regularly check your HVAC system. Some businesses offer a maintenance plan that includes ‘free’ visits from a technician for monthly or quarterly tune-ups. Many service plans include repair plans at discounted rates if any part of your HVAC should go wrong.

A professional maintenance contract will lower your total cost of ownership. They take out the surprise costs of emergency repairs

Your HVAC system is complex and should be attended to by a professional. Even if you decide that a maintenance plan is not for you, call a certified technician to repair your system when it needs attention.


A water leak from your air conditioning is a serious problem. If you suspect that part of your HVAC system is leaking or has issues, it is best not to wait for it to get worse – fix the problem immediately. 

There are several suspects regarding water leaks in your air conditioner. If you suspect you have a water leak, shut off the air conditioner and check these areas first.

Remember that paying attention to your HVAC and doing routine maintenance on it is the best way to prevent leaks from happening. Make sure you stay ahead of the problems and regularly inspect your system.

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