What Causes Air Conditioner Drip Pan To Overflow?

Your air conditioner has a drip pan. The drain pan collects the water from the evaporator coil during the cooling process. The excess moisture then moves to the outside of your house via the drain line. As a result, the condensate drain pan may overflow. This is not a normal occurrence. However, it would help to find out the cause of the overflow in the condensate drain pan.

What causes the AC Drip Pan to Overflow?

Many factors can cause a drip pan to overflow. One of the most common ones is a cracked condensate drain pan. Another important factor is a clogged drainpipe. Over time, the accumulation of solid waste may cause a clogged drain pipe and eventual overflow.

What is an Air Conditioner Drip Pan?

An air conditioner drip or drain pan is a small component of your system that sits right under the evaporator coils. Your air conditioning unit functions by cooling warm air.

During this process, water drips from the cold evaporator coils. This is the water vapor that is in hot air. This happens when the warm air penetrates the cool evaporator coil surface.

It is common for people to ask this question: where is the condensate drain pan located? The condensate pan is along the condensate drain line of your system. The condensate drain line carries the water inside your drain pan to the outside of your house.

Should my Exterior AC Drain Pipe be Dripping Water?

Your exterior AC drain pipe should be dripping water. Your air conditioner removes excess humidity as warm air passes over the evaporator coil. This process is critical for the air conditioning process to be complete. The air conditioner’s humidity from the air indoors turns into water. It is the water that drips from your drain line.

Expect about three to five gallons of water to drip from your evaporator coil onto the drain line every day. This amount may increase when the weather is humid. If the weather is less humid, the amount of excess water that drips from the line should be less.

If you see stagnant water in your drain pan, the chances are that you have a clogged condensate line. A clogged drain line causes water to accumulate and overflow from the drain pan.

How much Water should Drain from the Air Conditioner?

The actual amount of water that should be draining from your air conditioner varies. One of the most important factors is the climate.

If you live in a dry climate, expect a small amount of water to drain from your conditioning system every day. For example, you may have only five gallons of water from the external drain pipe.

If you live in humid areas, expect a large amount of water to drain from your air conditioning system every day. You may have as much as 20 gallons of water from the system daily.

The size and nature of the air conditioning system influence the condensate amount. Large air conditioners produce lots of excess water than small air conditioning systems. This is so because the big air conditioner processes large amounts of air.

Common Issues of AC Drip Pans 


The drip pan is located beneath the air handler. It collects the water that drips from the evaporator coil within the air handler part of your AC system. The condensate pan may be made of either metal or plastic.

It is common for a plastic drain pan to crack after some time. A cracked pan causes water pooling near the opening of the indoor component of your AC.


Overflows occur when a clog in the line leads to the drain system. Sometimes, a clog may appear in the condensate pan. For example, algae and mold usually grow in the condensate pan over time.

This may cause a clog in the condensate drain pan. As a result of the clogging, excess water begins to overflow from the pan.

Causes of AC Drip Pan Overflow 

Clogged Pipe

Mineral impurities, algae, and mildew in the water that flows through the drain line can cause a clogged pipe. The deposits accumulate inside the condensate pan or drain line for a long time.

They then interfere with the way water flows from the air conditioner’s condensate pan to the drain system through the drain pipe.

A clogged drain line or a soggy furnace causes many potential dangers to the home. First, it may damage the attic furnaces. This happens because of the excessive flow of water in the attic and surrounding area of your house. The damage may cost you a lot of money in repair works.

Also, a clogged line causes water to accumulate on the pan and eventually begins to overflow. You do not want water to start overflowing from the air conditioner’s condensate pan instead of flowing directly to the drainage system.

Frozen Evaporator Coil

Dust and other particles usually accumulate on the evaporator coils of air conditioners. This accumulation of dirt usually causes the evaporator coils to freeze. When the coils become frozen, the entire HVAC system exhibits peculiar signs.

For example, frozen coils cause an overflow in the secondary drain pan. In addition, the second drain pan of your AC unit begins to overflow after the first one. This happens because the cold coils of your AC unit fail to effectively remove water vapor from the air to the drain pan.

Wrong Installation

Wrong installation of your HVAC system will cause overflow problems. Your HVAC system has many components that work together to remove excess moisture from the air indoors and cool the home.

If you attempt to install the system yourself but end up missing a small detail, the entire air conditioning system may not work well. This is because you may fail to align the drain pan properly.

If the pan outlet is not directly below the condensate drain pan, the water will not flow properly outside the pan.

For example, a perfectly normal HVAC system has the condensate drain pan standing in an upright position. However, if your AC system has a tilted pan, water will begin to accumulate over time due to poor drainage.

It is good to have a trained technician install your HVAC system. The technician understands technical issues such as a vertical furnace installation versus a horizontal furnace installation.

Also, if your air conditioner’s condensate drain pan is tilted in the wrong direction, a technician can easily correct the problem for you.

Broken Condensate Pump

Heat transfer occurs in your air conditioning system’s evaporator coil and produces water droplets. The exchange occurs as warm air passes over the cold coils. The water then travels via a small pipe to the condensate drain pan of your system.

When the water in the condensate drain pan reaches a certain level, the condensate pump automatically activates and pushes the water.

If the condensate pump is broken, water from the evaporator coil will accumulate in the pan and drain lines. If you are sure that this is the cause of the overflow, call the air conditioning company.

How to Fix AC Drip Pan Overflow Problem

The method you use to fix a condensate pan overflow problem depends on the cause of the overflow.

Clogged pipe

If the problem results from a clogged drainpipe, you need to examine the pipe and unclog it for the overflowing to stop. You can do this by first turning on the AC thermostat and allowing it to run for about 30 minutes. You may then switch the power supply to the entire air conditioning system.

Open the inside of the system by removing the access panel. Using a flashlight, carefully examine the condensate pan and pipe for any signs of clogging. You may see debris that may have accumulated inside your system.

Once you have cleaned the condensate pan carefully and returned the access panel, your system should resume working normally. In some cases, you may have to change the air filter of your air conditioner for it to work perfectly.

If the overflow is because of a broken condensate pump, you need to have it fixed. Replacing a condensate pump is a straightforward process. However, if you are not familiar with the general HVAC system, it would be a good idea to let a technician handle it.

For example, you can call your air conditioning company and let them send over a technician to look at the condensate pump and replace it.

The System was not Installed Properly

There are many technical details that one can miss when installing the system. For example, one can miss properly supporting the condensate pan. This may make the pan sag.

Also, one may fail to properly install the secondary drain pan when using the horizontal application. If any of these issues are the main cause of an overflow, a technician can help you fix them.

Drip Pan for Air Conditioner Overflow FAQs

Does my AC need a Drip Pan?

Your AC unit needs a drain pan. The condensate drain pan collects water that drips from the condenser coils. The water comes from the heat transfer that occurs inside the condenser coils. This process is similar to ice water getting heat from warm air and starting to drip.

Where is the Overflow Pan on my Air Conditioner?

The general location of the overflow pan on your air conditioner is under the evaporator coils in the heat exchanger. Here, the condensate pan collects the dripping water through a small pipe. Then, the condensate pump triggers the pan to move the water to the outside drainage system.

How much Water should be in the AC Drain Pan?

The minimum amount of water in your AC pan is five gallons in a day. The maximum amount should be twenty gallons in a day. The actual amount of water that drips from your system varies with the climate conditions and the size of the AC system.

How do I Drain an AC Drain Pan?

You can drain a pan by using a vacuum cleaner to remove the clog and flushing it with a cleaning solution. This will prevent further overflow of the excess water that drips from the evaporator coils of your air conditioning system.


AC overflow causes unwanted issues, including a soggy furnace and excessive flow in the attic. It may also cause general water damage.

For example, a clogged pipe, broken condensate pump, or excessive overflow may cause the overflow. Also, a tilted pan may cause the problem. You need a technician to rectify these problems and prevent further overflow.