Air Conditioner Leaking Water: Causes And Fixes 2025

Leaking water in an air conditioner is a very common yet worrying issue to a homeowner. Water leaks are in most instances caused by the fact that the condensation that occurs during the cooling process is not draining. Water may accumulate around your indoor unit due to clogs, broken parts, or even frozen coils.

This, when uncontrolled, may lead to water damage and mould. Luckily, most of the reasons that lead to AC water leaks can be fixed by a DIY approach, whereas some of them need professional repair.

This paper describes the most common reasons why a residential air conditioner is leaking water and how to repair them or when to contact an HVAC specialist.

Signs Your Air Conditioner Is Leaking Water

Prevention of damages caused by an air conditioning water leak is important and early detection is the key. These are the symptoms to look out around your AC system:

• Water pooling or puddles: The most apparent is the water dripping or pooling around the indoor unit. The presence of puddles or wet areas on the floor, in the furnace closet, or near the air handler is a sign of a leak.
• Higher indoor humidity: When your house is more humid or stuffy than normal, it is possible that the AC is not getting rid of moisture. A dripping AC usually has a hard time dehumidifying.
• Water stains or damage: In the case of attic or ceiling installations, you may find stains on the walls or the ceiling. Leakage of water through vents or light fixtures is a warning sign of an AC leakage above.
• Stagnant water: Stagnant water may result in the growth of mildew or mold. The presence of a musty odor around the vents or unit may indicate that there has been a leakage of water over a long period of time and that there is a growth of mold.
• AC unexpectedly turning off: Most new models include a safety float switch that will turn off the AC when the condensate pan becomes full because of some drainage issue. When your AC shuts down and refuses to restart, it could be as a result of a float switch being activated by a water backup.
• Poor cooling or ice on the coils: A water leak may be preceded by poor cooling or by visible ice on the evaporator coil. The ice can spill in the drain pan and drip water when it melts.

One should not overlook these red flags. A water leak should not be ignored as it may cause severe damage to the home and the development of mold, which destroys walls, ceilings, or floors. As soon as you see water around your AC, do something to identify the reason and eliminate it to save your house and equipment.

Why Do Air Conditioners Leak Water?

The air conditioners automatically remove moisture in the air as they cool the air. When the warm air blows over the cold evaporator coil, the water vapor condenses into liquid. This condensation drains into a drain pan under the coil, and is removed out of the house through a condensate drain line. This water is safely taken out when everything is functioning well.

When it is hot and humid, you may find water dripping at the end of the drain line outside, that is just your AC dehumidifying. Nevertheless, you are not supposed to observe water leaking inside the house in normal circumstances. There are a few problems that may make the drainage process go wrong resulting in leaks within. The usual issues are blockages, broken components, or improper installation that does not allow the drainage. The following paragraphs describe the most common reasons why an AC leaks water and the way to fix each of them.

Common Causes of an Air Conditioner Leaking Water

Clogged Condensate Drain Line

Clogged condensate drain line is the number one cause of water around an indoor AC unit. The condensate line is a pipe (usually PVC) which removes the water that has been gathered in the drain pan. In the long run, this narrow pipe may be filled with algae, mold, dust and debris, which may lead to a blockage. When the line is blocked, water overflows in the drain pan. The surplus water will then seep out of the unit- usually onto the floor or through the ceiling close to the AC.

How to Fix: Condensate line clog is normally a do-it-yourself repair with the right procedure:

• Switch off the power of the AC: To be safe, turn off the thermostat and the breaker to the AC unit before doing any work on the drain.
• Unclog the drain: Find the drain line opening (usually a PVC pipe close to the indoor unit). Suck out the clog with a wet/dry vacuum on the end of the line, or push out debris with a long flexible brush. You might observe sludge or algae to emerge. Make sure the line is clear by pouring a small amount of water through it and make sure it flows freely to the outside.
• Clean the line: Run a 50/50 vinegar and water solution through the drain line to kill mold and algae. White vinegar is usually suggested because bleach will corrode certain pipes. Leave the solution to act 30 minutes and wash with water. This will assist in avoiding new growth.
• Restart and test: Switch the AC back on and see whether there is still water leaking. When the only problem was the clog, the leak should be stopped. Keep watching the area on the following day.

When you cannot unclog a very tough blockage or the line is not accessible, it is prudent to call an expert. A clogged condensate line can be flushed or replaced in a short time by an HVAC technician who has special tools to do so. To prevent this, homeowners may pour a cup of white vinegar into the drain line every few months to prevent the growth of algae (do this sparingly to prevent corrosion of the pipes).

Rusted or Cracked Drain Pan

The evaporator coil is placed on a drain pan that is placed directly underneath it to collect all the condensation that drips off. In case this pan is broken, the water will seep through it and not drain. A metal drain pan may rust out over the years of use or a plastic pan may crack. After that, the condensate does not hold and funnel correctly, which results in an air conditioner leaking water at the bottom. Leaking drain pans are also common in older AC units (15+ years) that are rusted.

How to Fix: Check the condensate pan (you may have to take off an access panel). In case you notice holes, cracks, or large rust, you have a drain pan problem:

• Temporary patch: If it is a small crack or pinhole, you can use a water-resistant epoxy or sealant as a temporary patch. Wash and dry the pan and seal the crack well and leave it to dry. Pour a little water to test and see that it holds.
• Permanent solution – change the pan: A pan that is very rusted or broken should be changed. The size and shape of the pan used in each AC model are different and therefore get the right replacement part. This could be a task that needs an HVAC expert to install, particularly when the pan is difficult to access below the coil. Leaks on the bottom of the unit will be permanently solved by replacing the drain pan.

Once the pan is filled, it is always advisable to check twice whether the new or repaired pan is draining into the condensate line. Pan rust or cracks can be detected early enough before a leak occurs by regular maintenance.

Disconnected or Loose Drain Line

Other times it is not a clogged drain but a disconnected condensate drain pipe. The drain line may become loose or detach itself due to vibration, improper installation or a bad repair job. Once that occurs, the condensed water will lack a directed route and will just drip around the unit. This may lead to serious water damages in case the unit is in an attic or above a ceiling.

How to Fix: In case you suspect that the drain line is loose, check the point at which the pipe joins the drain pan. You may find in certain instances that the pipe has fallen off its fitting, or was not fastened down:

• Reconnect the pipe firmly: Reconnect the drain line to its point of attachment at the pan and tighten any clamps. Apply PVC solvent cement when the joint was glued.
• Check alignment: The pipe should be sloping in the right direction to its outlet and not under tension. A loose or stressed drain pipe may come loose once more.

In case the line was not installed correctly initially or continues to loosen, then get a professional HVAC technician to check and fix it. They can make sure that all connections are secure and they may redesign the drain system in case it is necessary to avoid frequent disconnection.

Malfunctioning Condensate Pump

A small pump is often installed in most vertical or basement HVAC systems to pump condensate water out of the house. This condensate pump gathers water in drain pan into a reservoir. A float switch is used to turn the pump on when the water level is high to force water through a drain hose to the exterior. The reservoir may overflow and cause water to leak around the unit in case the pump fails or the float switch malfunctions. That is, your AC may be leaking just because the condensate pump is not getting rid of water as it is supposed to.

Troubleshooting: A pump problem can be fixed by a few steps:

• Power check: Ensure that the pump is plugged and the outlet is powered. An open breaker or an unplugged pump will clearly halt its functioning.
• Check the pump and float: Open the pump reservoir and check whether there is debris that could be blocking the float or the impeller. There are occasions when algae growth may stick the float switch. Clearing the reservoir and parts of the pump may make it functional again.
• Check the pump: Fill the pump reservoir with water slowly. In case the float goes up and the pump fails to turn on to discharge water, then the pump or float switch is probably faulty.

Since condensate pumps have electrical parts and certain parts that need to be replaced, repair is usually done by the professionals. In case the pump or the float switch is faulty, an HVAC technician can change the unit and make sure that the new pump is wired properly and works. Meanwhile, switch off the AC so that the reservoir does not keep overflowing.

Dirty Air Filter Leading to Frozen Coils

An AC depends on airflow. An air filter that is dirty or clogged will choke the system. Inadequate warm air over the evaporator coil causes the temperature of the coil to be too low and it may freeze. You may realize poor air circulation through the vents or the AC failing to cool. In the end, the coil becomes covered with ice.

When that ice subsequently melts (e.g. when the AC cycle is turned off, or when the ice accumulates to the point of preventing cooling), the drip pan can receive more water simultaneously than it can drain, and the water will overflow and leak.

How to Fix: The solution is to restore proper airflow:

• Shut off the AC to defrost: In case you notice that the evaporator coil is covered with ice, turn off the AC and run the fan (or leave the system off) to defrost the coil. Never chip at the ice, but simply have it melt out into the drain pan. Keep towels ready in case it overflows as it thaws.
• Change the air filter: Inspect your filter. In case it is dirty, change it with a new clean one. The majority of households ought to change or clean AC filters after every 1 to 3 months and more often during the summer when they are heavily used.
• Unblock any vents: Take care that your home does not have any blocked supply and return vents due to furniture, rugs, and dust. The proper air circulation in the house aids the AC to work well and avoids over-cooling of the coil.

Once the coil has thawed and you have replaced the filter with a clean one, restart the AC and check it to see whether there are leaks. The better airflow will help to avoid additional ice formation. Should the evaporator coil still freeze after this, then there is possibly another problem (i.e. low refrigerant).

Low Refrigerant Level or Refrigerant Leak

The other cause of ice on the evaporator coil is lack of enough refrigerant in the AC system. When there is low refrigerant (usually as a result of a leak in the coils or lines) the pressure in the evaporator coil will decrease, and the coil will be very cold. The air moisture is then condensed on the surface of the coil.

As with a clogged filter, when that ice melts it can flood the drain pan and cause water to drip into your house. Symptoms of low refrigerant are the AC running continuously without achieving the thermostat setting, hissing or bubbling sounds of the unit or ice on the refrigerant lines and evaporator coil.

How to Fix: Refrigerant is handled by EPA-certified technicians. In case you suspect a leak of the refrigerant (e.g. you have already resolved the airflow problem and the coil continues to freeze, or you hear hissing), you will have to contact a professional HVAC technician. The technician will:

• Locate and seal the leak: They will find and seal any leaks in the coil or lines using leak-detection equipment and seal them (in some cases by replacing parts of the tubing or the coil).
• Refill the system: After sealing, the refrigerant has to be refilled to the right level. Operating an AC with low refrigerant not only leads to freezing and leakage but it may also destroy the compressor which is the most costly part.

The evaporator coil will not ice up anymore after professional service and the leakage of water will stop. Refrigerant issues should be dealt with as soon as possible, since they can only get worse (and keep causing leaks) when ignored.

Excess Condensation on Ductwork or Vents

Air handler is not the only source of so-called AC leaks. Sometimes you may notice that water is dripping out of AC ceiling vents or ducts. This may be as a result of condensation of cold ducts or vent surfaces when they are exposed to warm and humid air. When your ductwork runs through a hot attic or crawlspace, and is not well insulated, the difference in temperatures may cause moisture in the air to condense on the outside of the ducts. The water can then drip down simulating a leak.

How to Fix: Solutions to excessive condensation (which is also referred to as sweating ducts) may include:

• Enhance duct insulation: All ducts which are accessible should be well insulated to ensure that warm air does not come into contact with cold duct surface. Install or add insulation to ducts where necessary, paying attention to the places in attics or the outside of the house.
• Lower the humidity indoors: Very high levels of humidity at home (more than ~60%) may also lead to condensation. Apply dehumidifiers or ventilation when necessary during the most humid days of summer.
• Ensure airflow: Ensure that the airflow of the AC is not blocked. Stagnant air in ducts that is very cold can promote condensation, and thus airflow and system balancing is important.

The condensation on ducts is not an AC failure in itself, but it may lead to water damage in case it is continuous. In case you notice continuous dripping of the ductwork or vents even after following these measures, it is possible to contact an HVAC specialist who will evaluate your duct insulation and the system in general.

Improper Installation or Unit Not Level

One of the most unexpected reasons of water leaks in a newer AC system is the poor installation. When the central air conditioner is not placed on an even surface, the condensate might not drain towards the drain and might overflow the pan side. Likewise, improper plumbing of the drain line (such as the drain pipe size or layout does not suit the unit) may also hinder the flow of water. Such installation problems can cause a brand new AC to leak water.

How to Fix: Problems with installation usually need the intervention of a qualified HVAC installer:

• Make the unit level: In case the indoor air handler or furnace is not level, then it must be leveled. This could be by shimming the unit or by putting a well leveled mounting pad underneath it. In the case of window AC, make sure that the unit is tilted a little bit back (outside) to make the water flow outside rather than inside the room.
• Adjust the drainage system: In case the drainage line routing or size is not right, a professional can adjust the drainage plumbing. They will make sure that the condensate line is always sloping downwards and that there are no blockages or drooping parts that water can be trapped.

Once a good installation repair is done, the AC is expected to drain. To prevent these avoidable leaks, install or move AC equipment using experienced, licensed HVAC professionals.

DIY Troubleshooting Steps for AC Water Leaks

In case of an AC leak, this is a simple step-by-step procedure that can be followed by a homeowner who is not afraid of doing simple maintenance:

1. Turn off power: Switch off air conditioner at the thermostat and the circuit breaker. This avoids electrical risks and prevents the leakage to deteriorate as you check.
2. Inspect the air filter: Find your return vent or air handler filter and look at it. In case the filter is full of dust, remove it and put a new one. Clean filter guarantees the correct airflow and can fix the freezing problem.
3. Check the drain pan: Look at the drain pan beneath the coil with a flashlight. Empty it (wet/dry vacuum or absorbent towels) in case it is filled with water. Looking at rust or cracks is a problem, a small crack can be temporarily sealed but a pan that is rusted out will have to be replaced.
4. Clean the condensate drain line: Locate the PVC drain line outlet (usually outside by the foundation or by the indoor unit). Clear any obstruction in the line with a wet/dry vac or a thin brush. Wash it out with a solution of vinegar and water so that it is clear.
5. Resume cooling and monitor: Replace power to the AC and run it. Check any new leaks after an hour of operation. In case the water problem was solved through the above steps, then you probably discovered the problem. Keep watching it on the following day.

Most of the simple causes such as clogs or dirty filters can be solved by these DIY steps. In case you do all the above and the AC continues to leak water, then the issue might be beyond your diagnosis.

When to Call a Professional HVAC Technician

Although a handy homeowner can repair most of the causes of an AC water leak, there are cases that definitely need the services of a professional. In the following cases, you are to call an HVAC technician:

• Refrigerant leak or low refrigerant: If you think there is a refrigerant problem, or you notice repeated ice on the coils even with good airflow, do not try to work with refrigerant yourself. The leak has to be repaired and the system recharged by a certified professional.
• Damaged condensate pumps or significant part failure: Broken electrical parts such as condensate pumps or float switches ought to be repaired by specialists. Likewise, in case the evaporator coil itself is damaged or extremely dirty, then professional service is required to repair it or clean it thoroughly.
• Mistakes in installation: In case you find out that your AC was installed improperly (e.g. it is not leveled or the drainage system is poorly designed), a professional can re-install or correct the unit. They are knowledgeable enough to make sure that everything is in code and working as it is supposed to.
• Constant or mystery leaks: When the water keeps reoccurring and you cannot find the source or you have attempted to fix it yourself with no luck, call in a professional. Constant leaks may be a sign of more serious problems which require professional help.
• Safety issues: In case the water that has been leaking has touched any electrical parts or made your system to go off unexpectedly, then it is safer to have a professional to determine the situation. Water and electricity are a lethal combination so do not take chances.

Keep in mind that a good repair in the future can cost you less than a big repair in the future. Not only will a professional resolve the immediate problem, but he or she will also inspect the possibility of any secondary damage (such as mold growth or electrical problems) that may require attention following a leak.

How to Avoid Being Ripped Off and Get a Fair Repair Price

It is not easy to find the right person to repair your air conditioner, some companies will give you the lowest prices since they are inexperienced or have bad reputations and others will charge you too much on the same job. That is why the most intelligent thing to do to receive quality repairs at a reasonable price is to compare the estimates of the best-rated local professionals. Visit each of them, get to know about their background and the experience of the technicians who will perform the work. Select a contractor who has a good experience in repairing air conditioners and has fair prices. You may speed up this process with the help of our Free Local Estimates service.

After completing a short form and sending it, you will soon receive a call of three of the best air conditioner repair and installation companies in your area. They are vetted in terms of experience and all of them are licensed and insured to protect you. Get started now to secure your home and wallet today by clicking below.

Preventive Maintenance to Avoid Water Leaks

The most appropriate approach is to avoid the occurrence of AC leaks. Routine maintenance makes your cooling system healthy. These are some of the preventive measures to prevent AC water leaks before they occur:

• Change filters: Put in a new air filter every 1-3 months during the cooling season. This will guarantee that the evaporator coil is not frozen due to the strong airflow. It also prevents the dust to settle on the coil and block the drain pan or line.
• Maintain the condensate line: Check the condensate drain occasionally to see whether it is blocked. To prevent the growth of algae, as a matter of practice, pour a cup of white vinegar down the drain line every few months. Make sure that the line is well sloped and the outlet of the drain outside is not blocked.
• Clean the evaporator coil and pan: Dust and grime on the evaporator coil may cause inefficiency as well as water problems. In annual maintenance, the technician should clean the coil and also clean the drain pan. A clean coil will permit the water to drip into the pan (rather than splashing off the dirt).
• Check ducts and insulation: Check that any ducts you can reach are well insulated, particularly those in attics or crawl spaces, to avoid condensation. Air leaks in the duct joints should be sealed to prevent the addition of extra humidity. When ducts are properly insulated, the possibility of water forming on them is minimized.
• Have tune-ups on your HVAC: Schedule an annual tune-up of your air conditioner with a professional to identify problems before they become severe. The technicians will inspect the drain pan and line, test the float switch, clean coils, and make sure that the system is operating efficiently. Surprise leaks can be prevented by regular maintenance.
• Put in a condensate overflow switch: This is also called a float switch and it switches off your AC when the water in the drain pan rises too high. You can prevent water damage by installing a float switch (assuming your system lacks one) and having it automatically shut down the AC before an overflow can happen.

These preventive measures can go a long way in ensuring that homeowners reduce the chances of an air conditioner leaking water. Being proactive in terms of maintenance does not only help avoid leaks but also prolongs the life of the AC and makes it work at its optimal efficiency. With a clean and well-maintained system, you will be able to have a cool and dry house throughout the summer without having to worry about the unwanted water damage.