HVAC Secondary Condensate Pan

The Importance of an HVAC Secondary Condensate Pan

One of the most important tasks your air conditioning system performs is removing condensation from the air. Without this feature, your home would stay humid year-round – unless you live in an actual desert.

That’s why when you start noticing the humidity increasing inside, you should always think about checking your HVAC system. It may have something to do with the condensate drain pan.

If you have no idea what we’re talking about, that’s okay. Unless you’re an HVAC technician yourself, you may have never heard those words put together in that way. Fortunately, that’s what we’re here for!

Written by Jeremy James

Jeremy James is a veteran of the U.S. Navy who has grown his family's HVAC business into one of the most successful home service businesses in Knoxville, TN. More than 20 years of experience in the HVAC and Engineering industries and passion for what we do has translated into our customer service, professionalism, and quality. LinkedIn

water overflowing from secondary condensate pan

How a Condensate Drain Pan Works

Your HVAC system cools the air when its evaporator coil fills with super-cooled refrigerant. As your home’s warm air passes through your air conditioning, the mixture of warm air and cool refrigerant creates condensation. Think about all the water that beads up along the outside of a cold glass of water on a scorching July afternoon – then multiply it times several thousand.

That water needs to go somewhere.

Your air conditioning unit uses the condensate drain pan to catch every bit of humidity and excess water that it removes from your indoor air. Then, it safely and effectively disposes of that water outside your home.

When it’s working properly, that is.

Where is the Drain Pan Located?

The condensate drain pan located beneath your evaporator coil is referred to as the primary drain pan. Your AC unit’s condensate drain pan is not an independent component of the system. It’s connected to the evaporator coil – depending on the type of furnace you have. Furnaces are usually installed vertically or horizontally, either in a closet, garage, or attic depending upon their position.

Once you know your furnace’s location, you’ll find your drain pan.

Why is a Secondary Condensate Drain Pan Needed?

While your secondary condensate drain pan is a very simple component of your HVAC system, it’s one of the most important parts. Without it, you could end up with severe water damage to ceilings due to overflow and many unwanted issues.

That’s why many HVAC units have a secondary drain pan – also called a backup drain pan. This pan is placed underneath the unit and is large enough to catch every drop of overflow water from the internal drain pan. Secondary drain pans also have their own condensate drain lines. Drain pans vary in size to accommodate vertical furnace installation or horizontal furnace installation.

The horizontal application can be tricky. The unit must be raised high enough to allow gravity drainage to work correctly. Furnaces in the upright position do not have this problem.

New secondary condensate pan

Common Issues You May Find with Your Air Conditioning Drain Pan

Condensate drain pans often come with rolled edges so that once enough water pools up inside of it, it’ll fall out into the secondary drain pan below. These condensate drain pans often include reinforced corners so they’ll stay sturdy and able to hold all the excess water in them securely.

However, even with rolled edges and reinforced corners, these pans can still suffer from some serious damage over time. Here’s how:


The majority of newer drain pans are made out of plastic, but the really old ones were made out of metal. As everyone knows, exposing metal to a lot of water over the years can lead it to rust and corrode significantly. Those rusty spots become damaged and eventually cause water leaks which should be fixed ASAP.


If you have a plastic drain pan, it can crack over time as a result of ever-changing temperatures. The weight of the water itself can also cause strain in most pans. Even the most minor cracks in the pans can let water seep through and cause damage to ceilings in your home – especially if your furnace and evaporator coil are located in your attic.

A cracked condensate drain pan is a significant repair. It could require removing your unit which would include ductwork, brazing, vacuum testing, etc.

One sign that you may have a problem is a brown water stain appears on your ceiling.

Water damage in attic from misaligned drain

Clogged Drain Line

The drain line itself can also clog. This can come from bacteria growth in the line or dust and debris buildup. Much of the debris comes from infrequent air filter changes. Since the drain pan catches all the water, homeowners may not realize what all is floating around in their drain pans. Then, it has to deliver that stuff outside the home. After enough time and debris, it’ll clog and water will pool above, causing overflow and costing homeowners an awful lot of money.

Many clogs can be difficult to access. Your technician may need additional time to search for and find the clog. Secondary drain pans should have pan float switches to prevent your AC from turning on if it isn't draining.

secondary condensate drain pan with water


As you can tell, it’s pretty crucial to have a secondary drain pan attached to your HVAC system to fight condensation. Without the proper system of condensate drain pans and secondary condensate drain pans, you might end up with a serious situation on your hands. If that’s the case, you’ll likely need to call in the professionals at once.

Call an HVAC Pro

Have an issue with your AC condensate drain pan or drain line? If you’re unsure or want a professional eye to take a look at your air conditioning system in Knoxville, TN, you’re in luck.

At Blue Water Climate Control, our HVAC technicians understand all the finer details about your heating and cooling system. We can take a look at your drain pans and determine if there are any cracks, rust, or clogs that need immediate attention. We’ll also discuss your options on everything our services will cover so you won’t need to worry about your air conditioning anytime in the near future.

Condensate pump sitting in secondary drain pan

Learn More

For more information on the secondary condensate drain pan or anything else in the HVAC industry, check out the Blue Water Climate Control blog each week!

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