Air Conditioner Leaking Water? (Learn Why & How To Fix It)

When you notice a water leak, it can cause a panic. When that leak is from your central air conditioner unit, that panic may escalate. The truth is, though, that there are only a few things that can cause a water leak from your AC system.

While it may be scary, there are things you can do to diagnose, solve and even prevent water leaks from happening. This article will examine those steps and procedures and help you get back to a normal day without your AC leaking or causing more damage.

Types of ACs & Associated Water Leakage

Water leaks are bothersome, and they can result in some serious damage if not handled promptly. The good news, however, is that there are only a few things that can cause an air conditioner to leak water.

Since the AC is not connected to a water source and does not use water to operate, it limits where the water is coming from and what can be causing the leak you see (or hear). Depending on the type of air conditioner, that cause can be slightly different.

Central/Mini Split AC
Goodman GSX14 Central Air Conditioner

Central HVAC units and mini split AC systems are the most common residential AC types. They are also the most susceptible to noticeable water leaks.

Partly because the systems are so large and partly because of how they are used, it is easier to create too much condensation or have the system running while in need of repair.

For these systems, there are two leading causes of water leaks. The first is a clogged or damaged drain pan, allowing the condensation to overflow or drain improperly.

The second main reason is ice build-up. Once the system is off and the ice melts, it causes a water leak.

Window AC

Window air conditioners drain water through the rear of the unit, either down a drain tube or just a small hole in the drain pan. It is highly common to see the drain pan dripping water or even being overflowed with various window AC models.

If the window unit is not installed correctly or level, that drain pan full of water can flow forward instead of back, resulting in water leaking out the front of the unit and into your home.

Portable AC

Portable air conditioners also use a drain line or a collection tank. If the tank is not emptied in a timely manner, it can overflow, resulting in a water leak. However, most modern units have sensors that will shut the unit off if the tank gets too full.

This doesn’t mean it can always detect ice accumulation from prolonged running or use during colder weather. While ice build-up is uncommon, compared to central ACs and window units, it can happen with portable AC units as well.

Car AC

Car air conditioners are the most common water leaking ACs you will find. Nothing creates a little panic or increased heart rate when you notice a large puddle under your car. However, it is actually quite common and nothing (usually) to be concerned about.

Cars do not have drain pans or lines for air conditioner condensation. Usually, the heat from the engine will evaporate most of the condensation. However, if left idling, or on extremely hot days, you may notice more water than usual. If the system is freezing up, it can be a sign of refrigerant leaks or airflow problems, though, so it is always wise to check it out.


An RV or motorhome’s AC system is similar to a central AC, just on a smaller scale. Usually, these systems are self-contained and aren’t as susceptible to leaking as the other AC types. When it does happen, it can be hard to notice.

The drain lines run under the units and deposit either on the ground or in some models into the gray or black water drains. You are more likely to hear the leak than to see it unless the leak is caused by freezing and ice melting. The usual culprit is blocked airflow from dirty filters or clogged coils.

Signs That Your Air Conditioner is Leaking Water

How, exactly, do you know your air conditioner is leaking? There are several tell-tale signs there is a problem. Obviously, looking at the AC while it is actively leaking is a big sign, but others are more subtle or hidden.

  • Hear running water.
    If you are hearing running water when nothing is on, you may have an AC leak. Water doesn’t always just drip out from the leak point. It can cling to surfaces and run down, with the help of gravity, to other parts of the home before it drips to the floor and creates a puddle.
  • Musty odors.
    Mold and mildew leave behind musty, stale odors. If you notice a strong, musty smell near your AC vents or the evaporator unit, you may have a water leak.
  • Swollen or cracked drywall.
    If the leak runs down support beams and through the walls, you may not ever see a puddle. However, paint and drywall don’t do well with moisture and can peel, swell or even crack when water is present.
  • Gurgling sounds when AC is running.
    When the air conditioner comes on, the blower fan in the evaporator unit creates a lot of airflow. This pressure can actually suction up water from puddles inside the unit, causing it to gurgle and splash.

How Much Leaking Water is Too Much?

By now, we know that air conditioners remove humidity and moisture from the air, create condensation, and need to be drained. Based on this knowledge, we also know that water is a part of the process. But how much water is too much?

The answer will depend on the type of AC you are using. An automotive air conditioner will drip to the ground when the car is parked, and it is common to see puddles of water between the front tires. However, if the puddle is excessively large or flowing constantly, it is too much.

All other residential and commercial air conditioners are different. They are all designed to be self-contained. The drip pans are connected to drain lines, which are routed to a drain or directly outside (window units, portable ACs, etc.).

In these cases, seeing any amount of water, dripping, collecting or pooling, is too much. Since you shouldn’t ever see any water leaks, even a small one is cause for concern. The cause and solution may be as simple as changing an air filter or cleaning condenser coils.

However, in most cases, the problem will be with the evaporator drain system. A clogged drain may require professional assistance to clean and clear effectively. If you are ever in doubt, it is always wise to consult an HVAC technician for diagnosis and repair options.

The Trouble with Excess Condensation from Air Conditioning

Water leaking from the AC is a problem. However, the underlying problem may be more serious than it seems. Not to mention that the leak can go on for some time before you notice it, which can result in even further damage.

Water Damage

Water leaks cause water damage. While this isn’t a surprise, what can be shocking is that you may not ever see the damage until it is too late. Water follows a path of least resistance, flowing from high to low.

This can take it along support beams, through wall bracers, and even into drywall. If the water leak lasts long enough or has high volume, it can cause irreparable structural damage to the home.

Mold, Mildew, and Pests

Water is also home to bacteria, mold and mildew, and other fungi. Shut off from sunlight in the walls or ceilings of your home, these spores can thrive and rapidly multiply. Black mold, in particular, can be dangerous to your health and respiratory system with long-term effects.

Once mold takes hold, it can also be extremely costly to remove. Often the affected area needs to be completely removed and rebuilt.

Read Related Article: Kinds of AC Window Mold

AC Shut Off

Water leaks put water and moisture where it doesn’t belong. This can include the electronics and wiring of your HVAC system. If water is allowed in the power supply lines, capacitors, or wiring, it can short the system, cause it to shut off, trip breakers, or worse.

Reasons Why Air Conditioners are Leaking Water & How to Fix Them

As we have discussed, there are two primary reasons for an air conditioner water leak, drain pan issues and ice formation. Below we will look at specific causes and give you options on how to fix them.

Clogged Condensate Drain Line

The drain line and drain pan are two of the most overlooked and undervalued pieces of an HVAC system. The pan itself is nothing more than a piece of sheet metal, and the drain line is usually a mix of rubber hose and PVC.

However, dirt, dust, and debris can accumulate on the evaporator coils, and as the condensate drips down, it takes the contaminates with it. Eventually, these contaminants will block the drain line at the pan level, or clog somewhere along the line.

Depending on your set up that drain line can be a few inches long or several dozen feet. Depending on where the clog happens, you may notice the clog-caused leak days or even weeks later.

To fix the issue, you need to flush the drain line until the clog is removed. High pressured air, or hot water is often used, though some chemical drain cleaners are also employed. After the drain is unclogged and flowing freely, you should investigate what causes the clog to prevent it from happening again. That lies in the drain pan.

Damaged or Rusted Drain Pan

The drain pan is only a piece of sheet metal, bent along the edges to make a quarter- to half-inch lip that connects to the drain line.

However, what most don’t realize is that this little piece of metal is crucial. It has to be flat, solid, enough off level to direct the water to the drain but not so off level that water sloshes over the lip.

When any aspect of this drain pan is out of alignment, it can cause major leaking issues. If the pan is damaged, it won’t be flat and may not be adequately aligned. This can cause water to flow to the wrong side, slosh over the edge or fall out through rust holes.

If the problem is the drain pan, a replacement can be difficult. In general, these pans are spot welded in place and aren’t designed to be removed.

However, you can buy replacements and if you are careful, replace them yourself. It is generally better to have an HVAC technician perform the work, though, so they can calibrate the angles and align the drain correctly.

Broken Condensate Pump

Many portable ACs, evaporative coolers, and window units have a condensate pump. Since these models are less likely to have a permanent drain feature, the pump moves the collected water from the holding take to the drain hose.

If the condensate pump isn’t working, the holding tank can overflow, causing leaks. This will generally appear in small portable AC units, which can be a problem since they mainly sit on carpeted floors or in bedrooms where a wet floor is more problematic.

If the pump is serviceable or the unit is still in warranty, you need to make a claim. If the unit is out of warranty, you can call a repair shop, though, with parts labor and handling fees, it may be cheaper to purchase a new unit.

Dirty Air Filter

Aside from the drain, the most significant cause of leaking is melting ice. Ice can form for many reasons, but the two biggest reasons are a dirty, damaged, or clogged air filter and low refrigerant levels (see below).

An air filter covers the intake area for the entire system. No air will enter the HVAC unit without first passing through the filter.

Of course, once the filter becomes too dirty, airflow will dwindle. When the system then tries to cool a lower air volume, not enough heat will be removed.

The result will almost always be iced-over evaporator coils.

When the system shuts off, the ice will begin to melt, and it can leak from almost anywhere. Even though some of the water will make it into the drain pan, it is more water than the pan is designed for, and you will have leaking areas all over your evaporator area.

The easiest to diagnose and fix, all you need to do is remove the air filter and replace it with a new one. Ensure that the airflow indicators are pointing the right way, and you will be all set.

Low Refrigerant

Low refrigerant is one of the most common reasons for an air conditioner freezing and icing over. The simple “fix” is to shut the AC off until the ice melts. However, this will only work until the unit freezes over again.

You will need an HVAC technician to inspect the system and find where the refrigerant leak is coming from, repair the leak and refill the system to the proper levels of refrigerant. Unfortunately, unless you hold an EPA 608 certification, you cannot handle, remove, refill or dispose of refrigerants, so this is not a DIY fix. It is still critical that you fix the problem, though.

Once the leak is stopped and the refrigerant levels are corrected, the icing and water leaks will stop.

Very Cold or Hot Temperatures

In some situations, older systems will produce excess condensation when the temperature is too high or too low. When the temp is too low, the system works harder to make the air even colder, removing more air moisture than it is designed for. This will overflow the drain pan.

When the temperature is too hot, the system will long cycle. Basically, it runs at a continuous rate, never shutting off long enough to cool and reset the system. Since it is constantly running, it is also continually creating condensate, which can fill and overflow the drain pan.

The fix is simple, though it may be uncomfortable. If the temp is too low, you only need to shut the system off until the temperature rises high enough to warrant running the AC.

Likewise, if the temperatures are too high and your system runs too much, you can raise the thermostat setting or turn the system off until temperatures lower, allowing the HVAC system to cycle normally.

When to Call an HVAC Specialist to Fix a Leaking AC

rheem air conditioner

Before you can fix or repair the cause of the water leak, you have to notice you have a leak. Short of stepping in a large, cold puddle on your floor, you may go a while before you find out you even have a leak.

While this can be detected with regular maintenance and routine inspection (see the following section), it is important to know when to call an HVAC professional to fix a leaking air conditioner.

Before you spend the money on professional inspections and repair procedures, you should check for yourself and fix or repair what is within your abilities. The first steps are to change the air filter and check the thermostat for problems.

Next, you will want to open the evaporator access panel (after shutting power to the HVAC system off at the circuit breakers). You can put your fingers in the drain pan to see if it is full. If it is, the drain is most likely clogged. With the help of a wet/dry vacuum, you can empty the pan and find the drain line. Removing debris and gunk may be all that is needed.

However, you may need to use drain cleaners or hot water to loosen any clogs inside the drain line itself. However, this isn’t always a great fix, even if a clogged drain is the problem. Even HVAC pros may need to unclog the drain several times before it is completely clear.

If, however, you have done all of the small things you can do to fix the problem, or you notice your system is icing over, it is time to contact an HVAC pro via the form we have included below. The longer you wait, the worse the situation will get, and the price of repairs will increase.

Tips on How to Keep Air Conditioners from Leaking Water

The best fix for a water leak in the AC system, of course, is to prevent it from happening at all. While this can be difficult, and you won’t be able to always prevent leaking issues with your AC, you can help.

  • Regular cleanings.
    You should have your system cleaned twice a year, once at the start of the season and again at the end. The cleaning should include both the evaporator and condenser units, coils, and fans.
  • Replace filters on time.
    Every 30 to 90 days (depending on the style of filter), you should remove, clean, or replace your air filter. This will maintain proper airflow and filtration of the system.
  • Don’t allow the system to run continuously.
    You can invest in a smart thermostat or just manually adjust temperature settings. However, keeping the system in a proper work cycle will help prevent condensation accumulation and future leaking.
  • Use drain pan tablets.
    Pan tablets will work to break up dust and debris that enters the pan. The tablets will usually last an entire season and help keep the pan and drain lines clean and unclogged.
  • Annual inspections.
    You should have your entire system inspected once a year. A professional inspection will last about 2 hours, and you will get a full report of any issues, problems, or potential failures.
  • Preventative maintenance.
    Using the inspection reports, you can spread out your maintenance and focus on issues that are more costly or critical first.

People Also Ask (FAQ)

Is water leaking from air conditioner dangerous?

Water leaking from the AC is just that, water. Except for the cases of ice melting, the water is just condensate and by itself not dangerous. However, water in an electrical system, especially a sealed system like your air conditioner, can cause some major problems. Water can short out electrical connections, blow motors, fuses and burn out capacitors. With arcing wires and burnt out electrical components, the risk of serious damage, injury, or even fire is possible.

Is it OK if its leaking outside only?

When the system runs, you will always notice condensate on the low pressure line (larger copper pipe). The pipe itself will be cold to the touch and is usually wet, even to the point of dripping. This is normal, and you can use foam insulation to help control the condensate. However, if the condensing unit has large puddles or flowing water, it is a sign of a much larger problem and should not be ignored.

Can I use my AC when it has water leaking?

A water leak is generally an external problem (meaning it isn’t internal to parts and motors). In itself, it isn’t much of a problem at first. However, if you let it continue, it will worsen and can potentially cause your entire system to shut down. While you can use the AC when it is leaking, it is highly recommended that you do not. Even if the leak doesn’t cause problems with the AC itself, it can cause structural damage to your home.

My AC is new, why is it leaking water?

While a newly installed AC shouldn’t leak water, there are several reasons why it can happen. It is possible you have the wrong sized AC for your home. A unit too small will work overtime, creating more condensation, and a unit too large can be too powerful for the amount of air running through it. It is also possible there was a problem with the install, such as the drain pan not being leveled correctly. If it is a new system, it will still be under warranty, and you should call to have it checked out.

Do AC leak sealers work?

AC leak sealers are not designed for water leaking and instead are made for refrigeration leaks. However, they should not ever be used. Even as a temporary fix, the chemicals and sealants inside these products can get into places they shouldn’t and cause more damage than they fix.

Is leaking Freon the same as leaking water?

A refrigerant leak can cause a water leak by freezing the system or creating ice on the coils. However, it is not the same thing as a water leak. As described in this article, water leaks are a specific effect and don’t have a link to the refrigerant.

My furnace is leaking water when AC is on – what should I do?

If you notice your furnace leaking while the AC is on, it can be an indication of a clogged drain (most likely) or a problem with the evaporator coils. First, you should turn the system off and clean up the water. Inspect the filter and condensate pump for clogs or damage. After everything is cleaned up, turn the system back on. If the water returns, the condensate pump or drain line is probably clogged or broken. An HVAC technician will be able to run diagnostics on the system to find the root of the problem.

How much will it cost to have a professional fix my leaking air conditioner?

The cost for a professional will vary on the location and time of year as well as the underlying nature of the problem. According to HomeAdvisor, a service call will range between $75 and $180. The cost of repairs will vary, depending on what is actually causing the leak. On average, most minor issues (clogs, damage to the drain pan, refrigerant leaks, etc.) will cost about $340 to fix.


Finding out your air conditioner is leaking water can be a scary sight. You may not know what is causing it or the extent of the damage. Further, it can be near impossible to determine how long it has been leaking.

While it is wise to call an HVAC professional (or fill in the form above) to diagnose and repair the leak, there are steps you can take to help fix the leak or even repair the damage yourself. This article covered everything you need to know to fix, repair, and prevent air conditioner water leaks before you need to call a technician.

Josh Mitchell

Josh Mitchell

My name is Josh and I am obsessed with DIY and improving my family home. HVAC topics can be tricky for homeowners so I decided to share my knowledge on the subject. When I am not working on DIY projects, you can find me at the beach or my local coffee shop.