Why Is My Air Filter Wet?

2017 Dec 22
Posted in: Air Quality
why is my air conditioner filter so dirty

So you’ve discovered that your HVAC air filter is wet and you’re wondering:

  1. Is this normal?
  2. If it’s not normal, what’s causing it and how do I stop it?

Well, first off, no—it’s not normal. During normal operation, your air conditioner/furnace filter should always remain dry. A wet filter is inefficient and spreads moisture throughout your ductwork and home, creating the perfect breeding ground for mildew and mold.

So what’s causing your air filter to get wet? Well, it’s most likely a clogged condensate drain line. Your condensate drain line is what catches all the moisture produced by your AC or furnace and funnels it away outdoors.

We’ll show you what you can do to fix the problem. But first, it’s helpful to know why your HVAC system is producing water in the first place. (Let’s take a look.)

Need professional help right away? Just contact us and we’ll send a tech right over.


A wet filter means a clogged condensate line

Both air conditioners and high-efficiency gas furnaces produce moisture during normal operation. Now, normally, that moisture safely drains away outside via a white PVC drain, called the “condensate drain line”.

The white PVC pipes (seen above) are the condensate drain lines that direct moisture outside.

But sometimes, these lines can become clogged with dirt or algae. And when that happens, water will back up and eventually overflow.

And because most AC and furnace filters are located right beside the condensate drain lines, any overflowing water will quickly reach and drench your air filter.

Related: Why Is My Air Conditioner Leaking Water?

So my air filter is wet, what now?

Step 1: Change your air filter ASAP.

There are 2 reasons why a wet air filter is harmful:

  1. It decreases the system’s efficiency. A filter is supposed to allow air through but not air pollutants (like dust, debris, dirt, pollen, etc.). But if the filter is wet, it won’t allow as much air to pass through the tightly woven material that comprises your filter. Over time, this causes the AC to work harder and longer. And that extra strain on motors and other components means more repairs and higher energy bills.
  2. It increases the risk of mold & mildew. If your filter is wet, it pushes excessive moisture into your ductwork and your home. This creates the perfect breeding ground for mold and mildew (especially during humid summer months).

Need help changing your furnace or AC filter? Just contact us and we’ll send out a professional to change your filter and clear your condensate drain.

Step 2: Try to clear the clog yourself.

To clear your AC condensate drain:

1. Locate the white PVC drain outside your home (seen below).

Your AC condensate drain line will be outside your home (usually near the outdoor AC unit) and is the tail end of a white PVC pipe.

2. Attach the end of a wet vac to the condensate drain. Cover the connection with duct tape or a towel to make it airtight.

3. Run the wet vac for 10 seconds at a time to try to suck the clog out.

4. Repeatedly run the wet vac until the clog loosens.

Need more detailed instructions? Just check out our blog, “What to Do If My Air Conditioner’s Drain Line Is Clogged?

Not up for this DIY challenge? Let us take care of it for you—just contact us.

To clear your furnace condensate drain, you’ll need to contact a professional. That’s because a furnace condensate drain is usually located in an attic/basement or crawl space, which can be dangerous for homeowners to navigate if they’re not familiar with the furnace set up.

Need help from a Phoenix tech?

Just contact us.

We’ll change your filter and fix the problem so that your HVAC system stays healthy—and you stay comfortable and worry-free.

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