Has Your House Got Dirty Sock Syndrome? Here’s How to Fix It.

Dirty Sock Syndrome

Ew. Your house stinks.

It’s not the garbage. You took it out last night. It’s not your kid’s sweaty laundry. You just washed everything, folded it, and put it away.

But it sure does smell like sweaty underwear. No, scratch that. It smells more like… *sniffs*… a dirty sock.

Your house probably has Dirty Sock Syndrome.

If you’re thinking this is an HVAC issue, you’d be correct. Here’s what’s happening: You’ve got a really dirty evaporator coil.

The evaporator coil is the air conditioning (or heat pump) coil inside your HVAC system’s air handler, or blower. Not only is the coil dirty – little microbial organisms are feeding on the dirt, dust, and other stuff that’s collected on it. That’s what’s causing the terrible smell.

Sometimes, you’ll have mold on the coil. Sometimes you won’t. One way or another, it’s going to stink.

Dirty Sock Syndrome tends to occur and reoccur during the shoulder seasons. Simply put, your HVAC system isn’t seeing much action. There are only short calls for cooling or heat. If there’s moisture on the coil, it will linger there in between cycles and encourage bacterial growth. Then the stink will blow into your home whenever the system starts up again.

It’s also a more common problem with heat pump systems. When you run a gas furnace in the fall, the heat is usually intense enough to kill off any microorganisms before you smell them.

But when the conditions are right, anyone can experience the fetid funk of the dreaded sock. Even people with gas furnaces.

Besides the horrific stench, what are the effects of Dirty Sock Syndrome?

Good news: There’s usually nothing major to worry about. You’ll periodically experience a nasty smel until you fix the problem. That’s all.

In the event you do have mold on your evaporator coil (and remember, that might not be why you’ve got the smell!), some of the spores could be entering your home. If anyone in your family has allergies or is otherwise sensitive to mold, this could be a problem.

Thankfully, Dirty Sock Syndrome typically doesn’t pose a danger. It’s just a serious annoyance.

For most people, most of the time, the effects of Dirty Sock Syndrome amount to…

  • A stinky house (duh)
  • An appointment with your HVAC company
  • Cleaning or replacing your evaporator coil
  • Preventative measures to help you avoid the problem going forward

Want to know more about coil cleaning, replacement, and Dirty Sock Syndrome prevention? Read on!

You might just need to clean the evaporator coil.

This is the best case scenario. Your HVAC technician might be able to clean the gunk off the coil with compressed air, brushes, and/or specialized commercial cleaning products.

When your tech can get the coil clean, you’re good to go! The only other thing to do is take steps to prevent the coil from getting dirty again (more on prevention in just a sec).

But sometimes, the coil simply won’t get clean. You can perform a superficial cleaning, but it’ll be hard to get enough gunk off of the coil to avoid future occurrences of Dirty Sock Syndrome.

Replacing the evaporator coil doesn’t have to be expensive.

Having your HVAC tech say, “Well, it looks like we need to replace the evaporator coil,” might sound scary. But if your system is still under warranty from the manufacturer – and most systems are warrantied for 10 years! – you might get a new coil for free.

At PV, we mostly install Trane HVAC systems. In the rare case when one of these systems becomes afflicted with Dirty Sock Syndrome, Trane sends a new coil coated with black epoxy. Because of the coating, less dirt, dust, and organic material builds up on the coil in the first place, leaving fewer opportunities for microbial growth.

Dirty Sock Syndrome is an environmental problem, not an equipment problem. It can happen to any manufacturer’s equipment. When you think about it that way, it’s actually pretty cool of Trane to send a replacement coil and cover it under their warranty since, you know… it wasn’t their equipment that failed!

Oh, and if we installed your HVAC system, our labor warranty will cover installation of the new coil. Bam! You just got a free evaporator coil, free installation and (probably) “cured” your home’s Dirty Sock Syndrome.

Nice clean coil? Check. Now stop the smell from coming back.

If you’ve ever had the flu, you probably wished you’d gotten a flu shot. Sure, the Tamiflu helped, but it would have been better not to have gotten sick in the first place.

Prevention = critical. For sickness and for HVAC.

Remember why you had microbial growth on your evaporator coil? Organic material of various sorts was clinging to it. You want to keep to keep that stuff from getting in your HVAC system in the first place! Here are the steps for doing so:

  1. Have your air ducts cleaned, if needed.
  2. Upgrade from a 1” air filter to a media filter.
  3. Seal your ductwork.
  4. Make sure your HVAC system drains water properly.
  5. Install UV lights that illuminate the evaporator coil inside your ducts.

First things first, determine whether your air ducts need to be cleaned. If you’ve got a thick layer of dust and grime inside your return ductwork, there’s a good chance some of that stuff is getting sucked into your air handler and collecting on your coil. Have those ducts professionally cleaned!

After that, it’s a good idea to upgrade your air filter to a media filter. These filters have more surface area than typical 1” filters and do a better job filtering air without a significant decrease in static pressure. When installed properly, they’re also far less likely to let air (and dust)! enter the system around the outside of the filter.

Now you want to be sure a leaky return duct isn’t causing your system to suck in excess dust and dirt. Have your ducts sealed by a home performance professional who knows how to minimize duct leakage.

Drainage matters, too. Is your drain line clean, and does it have the proper slope? Or is something preventing your system from draining condensate the way it’s supposed to? If moisture isn’t draining away from the coil, you’ll have Dirty Sock Syndrome again before you know it.

Finally – and you may not need to do this, but it’s a good idea – get UV lights that shine directly on your coil and prevent microbial growth from occurring. That way, you’re unlikely to experience Dirty Sock Syndrome again even if conditions inside your HVAC system are otherwise conducive to the proliferation of bacteria.

Dirty Sock Syndrome ain’t the end of the world…

But it sure is annoying! And gross.

When it happens to you, call your HVAC company to come have a look at your evaporator coil. Then, after treating the problem, take preventative measures to keep the smell from coming back.

Just don’t ignore Dirty Sock Syndrome if it goes away on its own! When the shoulder seasons are over, the smell often lessens or goes away completely. This doesn’t mean you’re off the hook. All the junk on your coil is still there, and it will stink again when the conditions are right.

Over time, the problem will get worse. So go ahead and get rid of it before it becomes harder – and more expensive – to resolve!