Why Is Your AC Drip Pan Full Of Water, Even Overflowing? (5 Fixes)

AC drip fan full of water is the worst. The air conditioner drip pan should never be full. If it is full, there is something wrong with your air conditioner. The culprits for a drip pan for air conditioner overflow are usually the same as the reasons why the drip pan is full of water.

Luckily, fixing an AC drip pan full of water is generally easy. In most cases, it should take you less than 15 minutes. The first thing that you have to do – and this is the trickiest part – is to diagnose why the drip pan is full of water.

Here’s what this looks like:

Let’s say you find a drip fan for the AC unit in the attic full of water. You know that all this water should be continuously draining somewhere. If it’s full, you immediately know something is wrong, and you have to look for the culprit.

The basic reason why the AC drip fan is full of water is simple in theory:

  1. Air conditioner accumulates water; this is the incoming flow.
  2. Air conditioner drains the accumulated water; this is the outgoing flow.

If the incoming flow is higher than the outgoing flow, after some time the drip pan will be full of water.

Here’s how to deal with it practically:

We are going to cover the 5 most common reasons why an AC tray is full of water. In more than 40% of cases, the culprit for an AC unit drip fan full of water is a clogged drain pipe (#1 below). That’s why we will cover this one first; if it’s not the clogged pipe, it might be that the pan is tilted wrong, the condensation pump is broken, and so on. Just go 1 by 1 and eliminate the culprit until you get to the specific diagnosis of what is causing your AC drip pan to be full of water.

With every culprit, we are going to explain how you can fix your air conditions. Example: If a clogged drain pipe is a cause, you have to open the AC up and unclog the wire with a piece of wire or a needle.

Don’t worry: In most cases, you will be able to fix the AC drip pan full of water yourself very quickly. In limited cases, when you have a broken condensation pump (#3 culprit) or low refrigerant levels, resulting in frozen evaporator coils and/or excessive flow (#5 culprit), you will have to consult an HVAC professional for repairs.

#1 Clogged Drain Pipe Causing AC Drip Pan To Be Full Of Water

Every air conditioner works as a dehumidifier as well. That means that it extracts the air moisture and effectively lowers the indoor relative humidity levels. Of course, the accumulated water has to go somewhere.

That’s why every AC has a drip pan that is continuously emptied via a specialized drainage pipe. When AC is working normally, the water will accumulate in the pan, and the drain pipe with continuously empty the water.

If you find an AC drip pan full of water, something in this process is amiss. In most cases, the culprit is a clogged drain pipe. Every drip pan has a drain pipe that has only one job:

Remove water from the drain pan.

If the drain pipe is partially or fully clogged, we will see a drip pan full of water. This is the most common occurrence in window air conditioners.

Solution: You have to unclog the drain. That sounds quite simple but, truth be told, it’s not the easiest job in the world. First of all, you have to unscrew the air conditioner’s front or back panel to get to the drainage pipe.

When you see the pipe, inspect if the pipe truly is clogged. You might see the accumulation of dust, algae, mold, or even signs of limescale in older air conditioning units.

If the pipe is clogged, you have to unclog it. The pipe is usually less than 1/2 inch wide. You will have to get something pointy like a piece of hard wire, a needle, or a very slim pencil. Make sure you clean the pipe in every direction. Even a partially clogged drain pipe can result in a drip fan full of water.

After you remove the cloggage, reassemble the air conditioner (put on the cover), and start it again. If the cloggage was adequately removed, the accumulated water will be effectively drained, and you have solved the problem of your air conditioner’s drip pan overflowing with water.

Now, if you don’t see the cloggage, the clogged drain pipe might not be the issue here. Here are other AC problems that may lead to a drip pan full of water:

#2 Drip Pan For Air Conditioner Overflow (Tilted Pan Problem)

In some cases, we see that the drip pan is not full of water but it is overflowing. That might seem to some that the pan is actually full of water.

The most common culprit here is a tilted pan. If you have had a window air conditioner for some years, chances are that the drip pan may be tilted during the winter. We see several drip pans for the AC unit in the attic full of water because the pan was inadequately installed; the pan is tilted beyond what it is supposed to be.

In both cases, the end of the drain pipe might be lifted. If the drain pipe is lifted, and the water is being accumulated in the other part of the pan, the pipe won’t be able to drain the pan, resulting in the AC drip pan overflowing.

Solution: Readjust the drip pan.

If the pan is unevenly placed (tilted), just readjust it. It should be balanced on all sides (ideally).

If you do have a tilted AC and you need a tilted AC, you can still have it tilted. However, you have to make sure that the drain pipe is located at the bottom of this tilt. That will enable the drain pipe to have access to water as soon as it accumulates.

After the drip pan readjustment, your drip pan should not be overflowing anymore.

#3 Broken Condensation Pump (Water Is Not Drain Effectively)

Some bigger HVAC units like furnaces and ducted air conditioners have a condensation pump. These bigger units can accumulate large amounts of water and cannot discharge this water effectively only by using gravity (as is the case with window AC units).

That’s why they come with a condensation pump. The condensation pump has only one function:

Effectively pump the accumulated water out of the drip pan.

In lots of cases when we see an AC drip pan overflowing (or even a furnace leaking; you can read more about furnace leakage here), the culprit is a broken condensation pump.

If the condensation pump is not doing its job, the accumulated water is not effectively pumped out of the drip pan and we will see either the drip pan is full of water or, if we are too late, the AC drip pan is already overflowing.

Solution: Replace the condensation pump.

This is not something homeowners should do themselves. With these bigger HVAC systems, it’s better to call an HVAC professional to have a look at the unit and replace the condensation pump if necessary. According to Home Guide, replacing a broken condensate pump can cost anywhere between $100 and $450.

#4 Incorrect Installation Can Lead To AC Drip Pan Overflowing

Improper installation can lead to a variety of issues with your air conditioner. One of these includes AC drip pan overflowing due to:

  • Incorrectly installed condensation pump (in bigger HVAC units).
  • Air conditioner is not being balanced correctly.
  • Inadequate air conditioner wiring.

All of these issues can cause your air conditioner to start leaking water out of the drip pan.

It’s very difficult to diagnose what exactly is causing the issue here. The general recommendation is to always use a licensed HVAC expert for all AC installations.

If you suspect that the AC drip pan is being flooded with water due to incorrect installation, you should call a licensed HVAC expert to make sure all the installations are correct and fix the mistakes that were potentially made when the unit was first installed.

Note: This issue happens with newer units. If a new AC unit’s drip pan is full of water, the incorrect installation is a likely culprit. If you have had an AC unit for 5, 10, 15-years, the #1 culprit is likely to be a clogged drain pipe.

#5 Low Refrigerant Levels (Frozen Evaporator Coils Or Excessive Flow)

The most troubling reason why an AC drip pan is overflowing are low refrigerant levels. This is a serious issue.

If your AC is leaking refrigerant, the refrigerant levels (and thereby refrigerant pressure) will decrease. As a first result, you will start noticing that your evaporator coil is starting to gather ice. In serious cases, you will even see an evaporator coil completely frozen (you will notice brown ice on the coils).

Frozen evaporator coils due to low refrigerant levels will inevitably cause a larger accumulation of water. This additional water dripping will cause your AC drip pan to overflow.

We talk about the excessive flow of AC condensate.

Now, how to fix an AC drip pan overflowing as a result of low refrigerant levels?

This is a serious issue and you should turn off the AC immediately. To fix the low refrigerant levels, you have to add the right refrigerant to your refrigerant lines. Before you do that, however, you should look for a leak. If the refrigerant levels are low, you have a leak. If that leak is not fixed, you can add refrigerant, but it will continue to leak.

Fixing leaking refrigerant lines is not something most of us can do by ourselves. With smaller units like window ACs, people with a lot of technical skills can try to fix it themselves. You can read an extensive article about how to go about fixing leaking refrigerant lines and replacing freon in window air conditioners here.

In most cases, you will have to call an HVAC expert to help you out.


Overall, we have seen that there are quite a lot of reasons why your AC drip pan may be full of water. Some of these culprits can cause the AC drip pan to start overflowing.

The key takeaway is this:

In most cases, your AC drip pan is full of water due to drain pipe cloggage (#1) or unbalanced AC (#2). You can fix this yourself.

If that is not the cause, the likely culprits include broken condensation pumps in larger HVAC units (#3), improper installation in new units (#4), or low refrigerant lines (#5). In all of these cases, you will probably need help from a licensed HVAC expert.

Hope all of this helps.

Leave a Comment