8 Most Common Reasons that your AC is Leaking

8 Most Common Reasons For A Leaking Indoor AC Unit

What are the 8 most common reasons for a leaking indoor AC unit, and how can you fix them?…and how can you fix them.

You can find out about the most frequent causes of air conditioner leaks and how to fix them instantly here.

It's very disconcerting to see water dripping down your air conditioning unit. You definitely don't want a big puddle inside, let alone the expensive repairs that would result from it! Even though your AC removes moisture from the air, this scenario isn't normal. Instead, water leaking from an AC may be a sign of a serious problem.

Immediately turn off your air conditioner if you notice water leaking, and contact HVAC support right away. Water accumulation can cause your AC to break down if you continue to use it. You don't need to panic if your AC unit is leaking water; however, you should address the issue immediately. A simple leak can be fixed by an HVAC technician and may not require extensive repairs.

Here, you'll learn about the most frequent reasons why an air conditioner drips, as well as how to immediately address them.

Why does an air conditioner collect water?

Your HVAC system controls both the temperature and the humidity level in your home. The evaporator coils in the indoor AC unit absorb the moisture from the humid air in your home. The cold evaporator coils condense the moisture from the air as it enters the system, making it less humid.

A drain pan collects the moisture drips, which leads to a condensate drain line. This line leads outside of your home and drains the water down. It is a concern when your air conditioner cannot remove excess moisture, leading to water leaking into your home.

Is It Possible to Use Your AC When Water Is Leaking?

Even if your air conditioning unit is leaking water, it will continue to function. However, your room may not be as cool as usual. Since you don't know why your air conditioner is leaking, it's always a good idea to turn it off as soon as you see water dripping from it.

what causes water leaks in ceiling

The AC may not be able to properly remove moisture if clogged drain lines, dirty air filters, or other issues are present. Here are some common AC issues that may cause the AC to leak water:

    • A clogged condensate drain line is one of the most frequent reasons for an AC to leak water. During the dehumidification process, your unit collects moisture along with dirt and debris.

Eventually, if the drain line is not cleaned, water will accumulate and block it, causing water to spill out of the drain pan right inside your house.

Current air conditioners have a cutoff switch that shuts down the system if a clogged condensation line is detected. This is a terrific approach to safeguard your home from water damage. If your machine doesn't have this feature, you'll need to take action yourself.

Mold caused by a leaking ac unit located in the attic.

A malfunctioning condensate pump or float switch is causing the system to flood.

A malfunctioning condensate pump or float switch is causing the system to flood.
When a central HVAC unit is located in a basement or faraway attic, it is not always very simple for water to flow out of the drain line. The condensate pump, therefore, is critical in removing water from the system.

When the water level in the condensate pump reservoir rises, the float switch on the pump is turned on. The condensate pump then drains water outside of your home.

Your air conditioner won’t expel water if the condensate pump is broken or the float switch has failed. If this happens, the water will accumulate and burst out of the unit. You must contact a repairman to have the condensate pump repaired or replaced, depending on the damage.

Your lens can get foggy because of condensation buildup.

In addition to its dehumidifying function, your air conditioner naturally produces condensation. Excessive condensation accumulation, on the other hand, may result in AC leakage from air vents or air ducts. Water may drip onto your insulation, resulting in damage. Further, it may also lead to mold development in air ducts and poor indoor air quality.


A damaged or rusted drain pan can cause problems with drain line backups.

The drain pan is located beneath the evaporator coils of the air conditioner or in the air handler to catch condensation as it drips. From here, the water flows into the drain line and outdoors. If the drain pan is damaged or rusted, the water will start to leak rather than flow into the drain line.

An air conditioning unit that is 15-20+ years old will show signs of aging, and one common manifestation is a rusty drain. A corroded drain pan can cause your AC to leak water over time.


This i an illustration of what an evaporator coil looks like before a cleaning. The evaporator is in-line with the blower motor, so a lot of debris and dirt tends to get stuck inside the coil if air isn't properly filtrated.

Frozen evaporator coils are one of the major causes of compressor failure.

When the refrigerant leaks or the airflow is blocked in the evaporator coils of your indoor unit, they may freeze up. This may cause moisture to accumulate and overflow the drain pan, resulting in water leakage.

There are two solutions to the problem.

Finding and addressing the cause of your air conditioner's iciness is crucial.

You must call a heating and cooling technician because you cannot repair this issue on your own. He must locate the leak, repair it, and refill the refrigerant.

Air filters that are clogged with debris can cause a variety of problems with your vehicle's engine.

The problem of water leaking from an AC can be caused by dirty air filters, as mentioned previously.

Filters ensure proper air circulation, trapping air pollutants while allowing clean air into your home. These particles, combined with dust, can build up inside the filters and eventually clog them completely. This clogging negatively affects your indoor air quality and can even harm your unit. Weak HVAC airflow is also caused.

The issue is that when air filters are clogged, warm air doesn’t move through easily. As a result, the evaporator coils freeze after some time, because the refrigerant is unable to absorb heat. Be prepared for a leaky puddle when the pipes thaw.



An incorrect AC installation is the most common cause for an AC that is prone to leaks.

A new AC was recently installed and is already leaking water, is often the installation being done improperly and which is why probably why it is leaking water.

Your AC and drain pipes might not be correctly installed, resulting in a water flow disturbance from the drain pan to the unit. As a consequence, your unit leaks water. It is also possible for a window air conditioner to leak water inside the house if it is installed completely flat. If it's not level, the condensation will spill water inside the house, creating a lot of mess.

With proper maintenance, most air conditioner leaking water issues may be prevented. During indoor and outdoor unit tuning, the technician looks for potential problems with major components. An annual tune-up also allows your air conditioner to operate at its maximum capacity, ensuring that your home stays comfortable all year long!

An AC that leaks water may be the result of a poorly connected drain line. An improperly installed, repaired, or loosened drain line may cause the line to disconnect. It's essential to pay for the best HVAC contractors possible, as the new equipment is going to only be as valuable as the company that installs it.

Water can pool on the floor or leak through the ceiling if the drain line is disconnected. The leakage source can vary depending on the location of your AC unit.

An answer:

Make sure to call a professional for repair and installation in the future to reconnect the drain line. HVAC support can reconnect the drain line.


For some protection from water damage, consider buying a wet switch or a water sensor of some sort that will attach to the condensate pan or piping, and can shut the equipment off if there's water that is sensed. This is a very common problem, and a small upgrade can save you a very large issue.

Jackson Systems & Supply has a ton of HVAC parts that can easily be installed by anyone if you're a do-it-yourself-er type of person. Check them out at this link here.

Silicon Valley Comfort
Johnathan towner

Owner of Silicon Valley Comfort | Senior Service Technician

I started my journey within the HVAC industry at 16 years old. I started vocational training at the central county occupational center in San Jose.

The program allowed high school students to earn credits for graduation by taking a special trades course for the second half of every weekday.

I took the program seriously, at least more than I did high school. The class had adults and high school students working together for 4 hours every day.

The program instructor chose me to be the class foreman after 6 months of my entry into the program. My responsibilities were to oversee other students on their daily projects. I led a small crew of other students while performing preventive maintenance on the rooftop HVAC units around campus.

After two and a half years, I obtained two certifications of industry recognition, I began working for a local contractor at 18 years old as an apprentice doing installations for a residential company out of Campbell CA...

...20 years later, Silicon Valley Comfort

Is it normal for an indoor AC to leak water?

This is an illustration of a mini-split type of wall mounted ac which is dripping water from it, likely caused from a clogged drain of dirty filters

Let’s answer some of the unknowns regarding the AC and its condensation drain.

Condensation is normal in an air conditioner, but it is not supposed to leak out of the evaporator coil; instead, it is supposed to drain through a PVC pipe to the outside. If you see water coming from anywhere else, you should call a technician to figure out what's wrong. Mold can become a serious problem, and if you have a central air and furnace system, water from the AC coil will often fall into the furnace, where it could rust the heat exchangers or get the control board wet, making it necessary to replace the control board.

  You should sign a maintenance agreement with a local HVAC company you trust. This will keep the equipment from breaking down or causing other unexpected things to happen, like dirt building up uncontrollably in the coils or mold growing in the areas around the units.

   Having a professional come out to your home or place of business at least once or twice a year to poke around the system and look for signs of an issue can prevent a minor problem from becoming a major one. They will clean up any equipment that has become out of control and has been abandoned.

   A preventive maintenance agreement also has advantages! As an example, consider the following…
Routine maintenance visits: You can schedule regular maintenance visits with your HVAC service provider, typically once or twice a year, with a preventive maintenance agreement to ensure that your system is running efficiently.

Priority service: Many HVAC service providers offer priority service to customers with preventive maintenance agreements, which means that if you experience a problem with your system, you will receive priority service and will be moved to the front of the line for repairs.

Reduced service call fees: Customers with preventive maintenance agreements frequently receive discounted rates on repairs and replacements.

Longer equipment life: By identifying and addressing potential problems before they become major issues, regular maintenance of your HVAC system can extend the life of your equipment.
Increased efficiency: Regular maintenance can increase the efficiency of your HVAC system, resulting in lower energy bills.

Improved indoor air quality: By identifying and addressing issues such as dirty air filters and mold or bacteria growth in the system, regular maintenance can help improve indoor air quality.

Peace of mind: With a preventive maintenance agreement, you can have peace of mind knowing that your HVAC system is being properly maintained and that you have a trusted service provider to call if any problems arise.

What are the common causes of a water leak coming from the indoor section of the AC?

An image of water on the floor to illustrate what would happen if the ac unit were to leak water out, due to a clogged drain

Many factors can cause water leaks in indoor air conditioning units.

Here are some common causes:
Clogged drain line: A clogged drain line is the most common cause of water leaks in indoor units. Over time, dirt, dust, and other debris can accumulate in the drain line, causing a blockage that prevents water from flowing out of the unit. Water leakage stemming from this reason can be prevented by either a better filtration system or regular replacements of the type of air filter you use in the system.

Dirty air filter: If the filter is not changed regularly, the dirt can bypass the filter and end up in the evaporator coil near the blower motor and wheel in your air handler or furnace. When this happens, the drain will often have dirty water due to the dirty evaporator coil, which removes moisture from the home and drains into the condensation drain; the dirt can drip along with it and plug the drain. Alternatively, a dirty air filter can restrict airflow, causing the evaporator coil to freeze. When the coil melts, the excess water can overflow the drip pan and leak from the unit.

Improper installation: If the unit is not installed correctly, it may not be level, which can cause water to pool and leak from the unit, as well as incorrectly sizing the equipment or not sizing the ductwork to be compatible with your new HVAC system will restrict airflow and cause the coil to freeze up, as it would with a dirty filtration system.

Damaged or rusted drip pan: The drip pan, which catches water that drips from the evaporator coil, can become damaged by ice expansion leading to a cracked primary condensation pan, or it can simply become rusted over time, causing leaks.

Low refrigerant levels: If the refrigerant levels in the system are too low, the evaporator coil may freeze, causing excess water to overflow and leak from the unit.

Improper equipment or duct sizing: If the unit is too large for the space it is cooling, it may not run long enough cycles before it shuts down because it will reach the temperature that you have set on the thermostat too quickly, in turn, the unit will not operate long enough cycles to be able to remove the moisture from the air, leading to excess water in the system that can cause leaks.

If you are experiencing water leaks from your indoor unit, It's important to take care of the problem immediately to prevent further damage to your home or system and the high chance that mold will grow. Contact Silicon Valley Comfort, and we'll be happy to take care of your home's heating, ventilation, and air conditioning system(s). It's also a good idea to have our technician figure out what's wrong and fix it.

Where do most AC units leak from?

The most common location for water to leak in an air conditioning unit, is at the indoor unit (e.g. evaporator coil), the evaporator coil and drip pan can become plugged up or cracked from excessive debris in the coil that wasn't filtered out properly or at all, and when airflow becomes too low, due to the dirty filter or coil, or if there are too many vents closed in the home, or if the return air is blocked with a piece of furniture; airflow velocity will drop and the coil will begin to form ice.. Leaks of water can happen in other places, but the indoor unit is by far the most often found location for these kinds of problems.
The evaporator coil is located within the indoor unit of the air conditioner itself. The moisture in the air will condense and collect on the evaporator coil as the warm air from your home is moved over the cold evaporator coil. The moisture will eventually make its way down into the drip pan, which has been designed to collect the water and channel it toward the drain line.

About The Author

Leave a Comment

Your email address will not be published. Required fields are marked *

This site uses Akismet to reduce spam. Learn how your comment data is processed.

Scroll to Top