Why Is My AC Filter Wet? Answers from a Florida Tech

July 09, 2020

Should My Heat Pump Run All The Time

If you go to change your air filter and notice that it’s wet or even damp, there’s probably a water leak coming from your internal AC unit or your condensate drain line.

The three most likely causes of the leak include:

  • Condensate drain line clog
  • Rusted or damaged drain pan
  • Frozen evaporator coil

Below, we’ll look at these issues in more detail, so you can get a better idea of what is making your AC filter wet and what you can do to fix it.

Rather get help from a professional? We’ve got you covered. We’ve been helping Tampa homeowners with AC issues for quite a few years, so no matter what’s going on, we can help. Learn more about the AC repair services we offer or request service!

First, replace your air filter

If your air filter is wet, the first thing you’ll want to do is replace it.

Think of your filter as a "bouncer" that only allows the good stuff (clean air and small particles) to enter your HVAC system and stops the bad stuff (large dust particles and harmful contaminants) from entering. But if the filter is wet, it won't allow enough air through your return vent. If there isn’t enough airflow to your AC, it can reduce your AC’s efficiency, eventually increasing your bills and putting undue strain on your AC’s internal parts.

In addition to reducing your AC’s efficiency, a wet air filter can also become a breeding ground for microorganisms like mold and bacteria. Your air filter’s job is to catch debris that is circulating in your home’s air and prevent it from entering your AC system. But, if your filter is wet, it gives those microorganisms a nice, damp place to grow, which can negatively impact your health and the health of your AC system.

So, bottom line, if your AC filter is wet, replace it.

3 possible reasons your AC filter is wet

Cause #1: Clogged condensate drain

The most likely reason your air filter is wet is a clogged condensate drain line.

Your AC condensate drain line is responsible for draining the moisture produced during normal AC operation outside. Note:Your AC doesn't just cool your home, it dehumidifies your home as well, which is why it produces moisture during normal operation.

But, if there is a clog or back up in the condensate line, it can cause the moisture to build up and leak down your indoor unit and onto the floor around it. In this process, your AC filter can get wet.

Evaporator Dehumidification Process Blocked

Think your condensate drain line is clogged? Try these steps...

  1. Locate the drain line (it’s usually near your outdoor AC unit)
  2. Attach a shop vac to the end of the line and creating a water-tight seal
  3. Turn the vac on for 2-3 minutes.

If you notice that there is a decent amount of debris in the shop vac after doing this, a clog in the drain line was probably your issue. Make sure your filter is dry, and if it continues to stay dry, problem solved. However, if this didn’t stop the leaking or you notice that your filter is wet again after you’ve replaced it, keep reading for a few other reasons this could be happening.

Cause #2: Leaking drain pan

Evaporator Coil Drain Pan

As we mentioned above, your AC is responsible for dehumidifying your home. As it dehumidifies your home, the AC uses the drain pan to collect all of the moisture it pulls out of the air. The moisture in the drain pan then slowly drains outside via the condensate drain line.

However, if the drain pan itself is cracked, water will also leak down the indoor unit, which can get your AC filter wet.

The most common reason your drain pan is leaking is due to old age. Because the drain pan is constantly full of moisture, over time it can rust and crack, which can cause a leak.

As pictured above, the drain pan sits directly underneath the evaporator coil, so it’s very hard to get to. So, if you think your issue may be a leaking drain pan, you’ll need a tech to come and replace your drain pan for you.

Cause #3: Frozen evaporator coil

The evaporator coil is the part of the AC system that absorbs heat from your home's air. The evaporator coils are filled with very cold refrigerant that absorbs both heat and moisture from the unconditioned air in your home.

But, there are a few issues that can cause your evaporator coil to get so cold that it freezes. And when that ice starts to melt, it can overflow the drain pan and leak, causing your air filter to become wet.

Example of a frozen evaporator coil.

So, what causes your evaporator coil to freeze?

  1. Restricted airflow- If there isn’t enough warm air passing over your evaporator coil, it can cause your coil to get so cold that it freezes. Restricted airflow is usually the result of a dirty air filter. However, it can also be a result of a dirty evaporator coil. If the coil has a layer of dust on it, it won’t be able to absorb as much heat as it usually can, which can make it so cold that it freezes. A tech will need to inspect the coil to determine whether the root problem is a dirty filter or dirty coils.
  2. A refrigerant leak- Over time, the AC's refrigerant coils can develop smalls holes which will result in refrigerant leaking from your AC system. When this happens, the refrigerant levels in the system drops, which causes the temperature of the refrigerant to also drop. Eventually, if refrigerant temperatures drop TOO low, the evaporator coil can freeze.

If you think a dirty evaporator coil or low refrigerant is your issue, you’ll need to contact a tech.

Still having issues with a wet filter? Call the most experienced pros in Tampa: Red Cap

If you’ve tried the suggestions above or you have one of the issues that require help from a pro, reach out to us. We have countless years of experience helping Tampa homeowners with their AC systems, so no matter what’s going on, we can help you.