Why Is Your AC Drip Pan Overflowing? [6 Causes & Fixes]

Are the overflowing AC condensate pan (also known as drain pan or drip pan) making your blood boil? If you don’t get cracking with fixing it right now, it will make so much mess inside! 

Luckily, as long as you can pinpoint the cause, repairing an AC with an overflowing drip pan is not rocket science in most cases.

I have included 6 common causes and solutions for an AC drip pan full of water or overflowing in the extended guide below. You can figure out how to handle this situation in a matter of minutes.

1. A clogged drain pipe

It is normal for a drip pan to have some water in it because the drip pan is in charge of catching water dripping off of the evaporator coil.

However, it shouldn’t be full of water as the water will continue to flow down the drain pipe and out of the air conditioner. 

Things change when the drain pipe is clogged. In this case, water will back up and accumulate in the drain pan. 

What clogs the pipe includes organic gunk, slime, algae, and other contaminants. If your AC has been used for years and the drain line hasn’t been maintained ever, chances for it is the culprit of an overflowing drain pan.

What to do?

Luckily, this problem is easy to fix. You can use a wire brush to dislodge the buildup in the hose and then pour some bleach or vinegar through the hose to kill any remaining molds and mildew. This will also ward off future growth.

2. A faulty AC float switch or wet switch

Many air conditioning systems these days have a float switch or wet switch installed in the condensate pan. This small component can detect the water level and shut off the machine when the pan is filled up with water.

That is to say, technically, the drip pan will never overflow as long as the float switch functions well. 

If you are sure that your machine has such a part inside, but the drain pan keeps filling up, the float switch could be to blame.

What to do?

The AC float switch could either be blocked or failed. You can first clean it off to see if the issue is mitigated. If not, replace it with a new switch, which is inexpensive. 

3. A damaged condensate pump

Not every air conditioning unit has a condensate pump, but the indoor unit in the basement or anywhere underground is likely to have a condensate pump because your AC can’t drain water by gravity. 

With time, more and more slime, dust, and dirt can settle down in the pump and clog it. Mechanical tear and wear can also cause it to malfunction.

When the water can’t be extracted by the pump, it will return to the drip pan and lead to overflowing.

What to do?

To put an end to this problem, your best bet is to replace it. Since you can easily access it, you can try to replace it on your own if you have some repair experience. 

4. Frozen evaporator coil

frozen evaporator coil

Since the size of the drain pipe is fixed, it is only able to drain a certain amount of water per unit time. If the evaporator coil of your AC unit is frozen, it will create excessive flow when the ice starts to thaw.

When the drain line can’t remove enough water in time, the overflow in the pan will occur. 

What to do?

Low refrigerant levels and dirty air filters are two common causes of frozen coils.

If the filthy filter is the culprit, you can solve this problem by removing, washing, and then reinserting the filter.

Things will become a bit more complicated when the refrigerant is the source of the problem. You can call a certified HVAC expert to locate the leak and recharge your AC.

It is not allowed to recharge your AC in many states because refrigerant is dangerous for your health and the environment.

5. Tilted drip pan

Occasionally, you will notice that your AC drip pan is overflowing but is not full of water. It often occurs when the pan is tilted. 

Due to extreme weather, tear and wear, corrosion, or rust, the drip pan can become warped. Poor installation can also result in a misaligned pan.

What to do?

You can try to solve the problem by readjusting the position of the drip pan. This often happens when you just got a brand-new AC installed. If the drip pan is out of shape, your best bet is to get a new unit.

6. Your air conditioner is not level

At the beginning of the cooling season, you may have installed your window AC or wall AC yourself.

This can save you a bunch of money. Nevertheless, you will end up getting a unit that is not balanced. 

When the machine is not level, the AC condensate pan will not stay in the right position, causing the water to overflow and get all over the place.

What to do?

You can try to fine-tune the air conditioner to see if the case is remedied. If it doesn’t work, you should call a certified HVAC expert to adjust the position for you.


Thank you so much for sticking with me all the way to the end. If you encounter an AC drip pan that is full of water or even overflowing, you can solve it by working through the problems I mentioned in this piece. 

While a clogged pipe could be the main culprit, a faulty condensate pump could be to blame sometimes. But anywhere, you can fix it in a short time on your own or with the assistance of a certified HVAC professional.

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Liz Yang is the founder of Airsmartly. She has been working at home for a few years and realizes that the performance of the HVAC system plays such an important role in our life. She has tested a lot of products in person, like humidifiers, air purifiers, dehumidifiers, and ACs, and wants to share tips about using or troubleshooting these products with you. Her uncle is an HVAC expert with over 30 years of experience in the field, and often offers assistance when she is unsure how to handle a situation. He is also in charge of reviewing the articles on this site.