Why Is My AC Drain Pan Full of Water?

What Does This Mean For you?

Does this mean you should not buy the home? Of course not.

If you are thinking of buying a home, you should definitely have a home inspection performed by Imperial Pro Inspection before you agree to the purchase. One of the things that the inspector may inform you of following the inspection is that the drain pan is full of water or has indications of previous water/rust. Does this mean you should not buy the home? Of course not. While a drain pan full of water is a sign that there is an issue with your AC, you might be able to do a quick do-it-yourself (DIY) repair. Of course, we always recommend that the HVAC system be further evaluated by a licensed HVAC professional.

The Drainpipe is Clogged

When an air conditioner’s drain pan is full of water, the most common culprit is a clogged drainpipe. Inside the refrigerant coils and pipes is a breeding ground for algae, mold, and the like. Overtime, algae and mold can clog the drainpipe and cause water to build up and leak into the drain pan. Although a clogged drainpipe can be an easy fix, it’s important to address the issue right away or else it could cause a mechanical problem.

How to Unclog the Drainpipe

Unclogging the drainpipe is relatively simple. Start by turning off the power supply to your air conditioner. Once the AC is off, inspect the tubing on the unit, making sure there aren’t any leaks, cracks, or other problems with the drain line. If you do find any issue, replace the drain line or faulty pieces. After the pieces have been replaced, remove any water that’s collected in the drain pan (hint: it’s easiest to remove any standing water with a wet-dry vacuum).

Once the water and any residue have been removed, it’s time to unclog. Remove the PVC cap from the drainpipe and clear the clog using a wire brush. It’s also a good idea to add a little bleach into the pipe once the clog is cleared—this will remove any algae or mold that may be contributing to the problem. Replace the PVC cap and proceed to test your air conditioner.

3 Reasons Your Air Conditioner’s Drain Pan is Full of Water

The Drain Pipe Is Clogged

A clogged drain pipe is the most common cause of standing water in the drain pan. As air passes over the evaporator coils in your air conditioner, it cools down and loses some of its humidity. This humidity is left behind in the form of condensation on the coils. The condensation drips off into the condensate drain pain and exits the system through the drain line.

Unfortunately, water isn’t the only thing that’s often left behind on the evaporator coil. The air that blows over these coils can leave behind dust and dirt as well. If the dirt drips off in the water, it can move down the drain line and ultimately cause a clog. Although this is a fairly straightforward problem, it’s best to contact one of our experienced technicians for this AC repair to make sure the job is handled right and there are no other issues going on.

The Evaporator Coil Is Frozen

A frozen evaporator coil can lead to dripping water that will leave telltale signs of moisture in your drain pan. The evaporator coil is most likely to freeze if your refrigerant levels are low. If you’re dealing with low refrigerant levels, this often indicates a refrigerant leak somewhere in the system.

Your System Wasn’t Installed Properly

If your air conditioner wasn’t installed properly, the drain pan may be angled in the wrong direction. Novices or those attempting a DIY installation might miss this simple yet essential alignment. The outlet for the drain should be on the lower side of the pan so that water flows toward it. If the outlet is on the opposite side of the pan, water will pool before draining.

The drain pan also requires stable supports underneath it to keep the pan in place and support the bottom. Without these, the pan might sag, creating room for water to pool.


If this DIY repair doesn’t work for you, call a professional. In fact, we always recommend that the HVAC system be further evaluated by a licensed HVAC professional if there is water in the drain pan. Air conditioning systems are expensive investments, so treat yours kindly! If your drain pan is full of water and you can’t figure out why, let a professional figure it out.

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