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Ever Heard of Dirty Sock Syndrome?

an air vent blowing out smelly air because the unit has developed dirty sock syndrome

It’s never a good thing to catch a whiff of a foul smell coming from your home. It’s even worse when you can’t name it or find it. It seems familiar, like gym socks that fell behind the washing machine. But that isn’t quite it. A quick check of the laundry room finds everything in order.

You know when the cat’s litter box needs changing, or if the laundry has been sitting in the hamper too long. A fragrant trash bin is easily identified. Maybe the house just needs a good cleaning? No, even after the kitchen, bathroom and floors get a good scrubbing, the off-putting scent lingers.

Once you have run through the list of usual suspects and still haven’t discovered the source, you might want to zero in on your HVAC system. Your house might have caught a case of dirty sock syndrome!

Why Is the House So Smelly?

Your home’s heating and cooling system gets a pretty good workout when temperatures are very high or very low. When it is running often, condensation builds up in the unit. That moisture attracts dust to the evaporator coil, and bacteria and fungus thrive in this environment.

In seasons where temperatures are more moderate and the system isn’t kicking on very often, the microbial buildup explodes. Then, when you turn the unit on, you often will catch a musty, moldy odor. Such a smell is normal when you first turn on an air conditioning system that has been off for a while. If this odor doesn’t go away or is appearing every time the system comes on, dirty sock syndrome is often the cause. Unfortunately, your HVAC system will push this air throughout your home, heating or cooling as necessary. And, it takes that smell along for the ride.

There are a few different areas in your system where dirty sock syndrome may develop.

The Evaporator Coil

The evaporator coil is the mechanism where the AC’s refrigerant absorbs the heat from the air. Basically, it is the source of the wonderful cool air that the system pumps throughout your space. This is why any bacteria or fungus at all can trigger something that makes your nose twitch. Once that growth starts, it will only get worse if you don’t take care of the issue. A dirty coil doesn’t just smell: It also makes the air conditioner work harder to cool the air and it can take longer to come to a comfortable temperature. That isn’t something you want to wait on if it’s a hot summer day! On top of that, this problem can lead to high electric bills.

The Air Filter

Another component of your system that can contribute to a dirty coil—and dirty sock syndrome—is a dirty air filter. Generally, you should change your filter twice a year to keep things running smoothly. Again, if you live in an area that is very windy or dusty, or someplace where pollen is a problem, you will want to swap the filter out for a new one more often.

A dirty air filter is just another place for dust to gather, and all of that dust will eventually find its way to the evaporator coil. So keeping a clean filter is a great way to keep dirty sock syndrome from making a return visit!

The kind of filter you choose also makes a difference. You can find filters that are washable, but even those won’t last forever and will lose effectiveness over time. You also can pick up a fairly inexpensive filter, but generally, you will get what you pay for. Cheaper filters have to be changed more often, and they don’t filter out as many particles as a higher-quality one. If the filter isn’t catching dust and pollen, where does it go? Into the air you and your family breathe every day.

If you or anyone else in your house suffer from allergies or have asthma or other breathing issues, you definitely want to keep the air inside your home as clean and fresh as possible. So dirty sock syndrome is about more than just a bad smell: It also is a sign that extra irritants are floating around in the air, ready to get into your eyes and nose and make you feel less than ideal.

Your AC specialist will be able to show you options to clear the air, including high-performance filters that might be a great choice for your home if dust buildup continues to be a problem. High-performance filters also don’t have to be changed quite as often, making it worth the extra cost.

The AC Drain Line

Your problem might lie in your AC drain line. This line helps keep condensation from sticking around inside the unit. It is normal for water vapor in the air to turn to water droplets when it hits the cooling coil in your HVAC unit. Those drops make their way to a drain pan, which catches the water and allows it to safely flow into a drain line.

However, if your line is clogged, that water has no place to go. Not only will backed-up water make a mess, but a clog here can cause quite a smell. The odor might show up near your system’s inside unit or it might be more noticeable near your registers, where the cool or warm air pushes out into your home.

If you smell something suspect, check around your inside unit for any standing water, or water damage to the walls or flooring where the inside part of the system is housed. A water leak coming from your AC is cause for alarm. If you’re having difficulty diagnosing your AC’s smell, you can always contact a pro. They have the tools and experience needed to get to the bottom of the problem efficiently.

While changing your air filters is a relatively easy fix, dealing with a dirty evaporator coil or a clogged drain line is a different story.

a living room leading into a kitchen

How To Clean Your Evaporator Coil

So we know that a dirty evaporator coil can be the source of dirty sock syndrome. Where is the coil, exactly what does it do and what can you do to clean it?

Your AC’s evaporator coil is located near the air handler, in the inside portion of your HVAC system. So, if it’s getting dirty, you can just clean it, right? You might be able to access it on your own, but it certainly isn’t an easy job. The evaporator coil sits deep inside the casing of the unit. Your best bet is to contact a professional to open up the air conditioner and see if the coil is dirty and whether it can be cleaned.

However, if you want to try it yourself, you can try one of these techniques:

  • Buy a commercial cleaner and follow the instructions on the label. Typically, you’ll need to let the cleaner sit and foam until the foam and debris drain away. Keep reapplying the cleaner until the coils are clean.
  • If you would prefer to avoid commercial cleaners, you can use a mild detergent and water. Just mix some detergent and water in a spray bottle and spray the solution onto the coils. Give the solution a few minutes to loosen up the buildup of grime. Then, wipe away any dirt and debris and reapply as needed.
  • If your coils are heavily soiled, you may need to use heavy-duty chemicals. At this point, it will likely be easier to contact a licensed professional.

How Often Should You Clean the Coil?

Ideally, your evaporator coil should be cleaned once a year, unless you live in a climate where wind or dust are frequent problems. However, it can be human nature to think of cleaning something only when a problem crops up, and evaporator coil maintenance is no different. In order to prevent trouble—which always seems to happen on the days you need your system the most—the safe and smart bet is to set up a regular maintenance schedule for your entire system.

AC professionals offer annual plans that include a set number of visits for one price. During the visits, one of the things your technician will check is the condition of your evaporator coil. If cleaning is needed, a professional has the tools and experience to take care of it easily. Less work for you, and better health for your air conditioner!

Something else to note: There are instances in which the evaporator coil cannot be cleaned well enough to work efficiently. Your AC professional will be able to inspect your coil, determine whether it can be cleaned and if not, what other options you have to get your AC into tip-top shape.

a living room with a white couch and blue pillows

AC Drain Line Clogged: Fixing and Preventing This Problem

Keeping your drain line clear requires some occasional care. A couple of times a year, you should check the outlet of the line and make sure it isn’t full of leaves, dirt, pet hair or other material. If it has a blockage, you are going to have to get it out to keep everything flowing as it should. Once you have cleared the line, you will need to flush it out with vinegar to keep mold from forming. Vinegar is a better choice than bleach, as that chemical can damage copper tubing and also cause a mess on your flooring if it spills.

This is another job where having an annual AC maintenance contract in place is very helpful. At each scheduled visit, your professional technician will check the drain line inside and out and unclog it as necessary. They can also check for any other necessary AC repairs. Home maintenance takes time and effort. Leaving your HVAC upkeep to a professional leaves you more time to do the things you enjoy, all while giving you the peace of mind knowing your system is in the best shape possible and you can breathe easy.

ABC Can Remedy Dirty Sock Syndrome 

Nobody wants a smelly heating and air conditioning unit. Instead of trying to diagnose and fix this issue yourself, contact ABC Home & Commercial Services. One of our licensed professionals will get to the root of the problem and fix it. In addition to air conditioning and heating repair, we offer ongoing AC maintenance, so you don’t have to worry about this smell coming back.

Tom Riggs

Tom Riggs is the Division Manager for Mechanical Services, overseeing sales and operations for HVAC, Plumbing, Electrical, Appliance Repair and Water Quality for all ABC Austin branches. He joined ABC in 2014. Before ABC, he was an HVAC Service Technician, HVAC Comfort Advisor/Sales and Operations Manager. Tom attended Universal Technical Institute. He's an avid outdoorsman and enjoys country living with his wife and two sons.

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