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Carrier Furnace Leaking Water? 4 Common Causes + What To Do

Water leaking from your Carrier furnace’s compartments, vents, or ductwork is a concerning problem. It can also be a sign of a larger problem, but the fixes are often more straightforward than you think. 

Your Carrier furnace is leaking water because of a poorly fitted drain pipe, leaking humidifier, worn-out rubber coupling, or a corroded heat exchanger. Fix the problem by checking the condensate pipe fittings, inspecting the heat exchanger and humidifier, and replacing the rubber coupling.

This article will guide you through the troubleshooting process for your Carrier furnace to see why it’s leaking. Moreover, I’ll explain how to fix each issue so that you can avoid having a dangerous electrical hazard in your home.

Incorrect Condensate Drain Pipe Fitting

We’ll start with the pipe that drains the condensate line. The pipe is fitted to the end of the condensate pump. It’s not part of the standard condensate line; the condensate line consists of white pipes, while the drainpipe is black. Liquids moved from the furnace to the condensate trap are drained through this pipe. 

When there’s a problem with the pipe’s fitting, condensate may push back into the condensate line. This can cause the Carrier furnace to leak water at the condensate assembly. If the liquids are pushed back too far due to a build-up, water can start to leak from the furnace too. 

Sometimes, opening up the furnace door may reveal a puddle of water collecting at the bottom of the main compartment. 

How To Fix

Fixing the fit of the condensate drain pipe is an effective fix for this particular problem. Start by checking whether this is the cause behind the furnace leaking water:

  1. Locate the condensate assembly in your furnace. The assembly consists of a condensate line, pump, trap, and drain pipe. 
  2. Take a look at where the drain pipe connects to the trap. Check how it’s fitted by gently wiggling the pipe to see if it’s lose. 
  3. While checking for a loose connection, it’s a good idea to ensure the pipe isn’t clogged. 
  4. If you see a clog, turn the furnace is off, remove the pipe, and run some hot water through it.
  5. When placing the pipe back into its position, fasten it tightly. 

The video below shows you how to clean the condensate drain:

Leaking Humidifier

There are times when the furnace’s water leak doesn’t originate from the HVAC system itself. If you have a humidifier, it’s probably connected to your furnace. The idea here is to add moisture to the air blown throughout your home to make the air more comfortable to breathe. 

Condensation occurs in the humidifier too. After all, it’s a device that creates condensation. Maybe the water you see is coming from the humidifier, not the furnace. In this case, water from the humidifier is dripping into the furnace. The water may start collecting in the duct line and the furnace itself, depending on where the leak occurs. 

How To Fix

This situation calls for a check-up of your humidifier instead of the furnace. If you regularly inspect the furnace for leaks, add the humidifier into your routine.

Take a closer look at the entire humidifier system. See if you can find areas of the humidifier that are also leaking water. 

If it’s indeed leaking water, take a closer look. Perhaps there is a blockage in its connection to the furnace. In such situations, you want to find what’s causing the blockage and address the problem. 

Worn-Out Rubber Coupling 

There’s a rubber seal in your condensate drain system. It ensures pipes fit tightly onto other parts of the furnace — particularly the condensate trap, pump, and drain. 

The rubber coupling can wear out over time. When this happens, leaks can occur in the condensate system. The coupling ages and thins out over time. This leads to less effective seals in the connections. If a leak occurs near the rubber coupling, condensate won’t move toward the drainpipe effectively. 

How To Fix

There is no way to fix a worn-out rubber coupling. Trying to insulate the areas with silicone is ineffective and can only lead to more problems in the future. With this in mind, let’s see what you have to do:

  1. Inspect all rubber couplings in your furnace to see if there are any leaks.
  2. Turn off the entire furnace. 
  3. Disconnect the condensate pipes.
  4. Inspect the rubber coupling fitted at the end. Throw it away if it’s worn-out, torn, or feels flimsy.
  5. Replace the rubber couplings. 
  6. Reassemble everything and see if the leaks have been resolved. 

Corroded Heat Exchanger

Apart from the condensate system and the humidifier, you should also take a closer look at the heat exchanger. This particular problem is unlikely to occur with newer Caririer models. However, if you have an older furnace, you need to look for signs of damage and corrosion on your heat exchanger. 

The heat exchanger ensures combustion gases don’t get into your home.

Since the heat exchanger is made of metal, it can rust and corrode fairly easily.

The corrosion can cause a leak of combustion gases into your ductwork. Your family will be exposed to harmful toxins. 

Secondly, combustion gases will start to accumulate in the furnace and ductwork. This increases condensation, causing a leak. 

How To Fix

When the heat exchanger is damaged or corroded, don’t try to fix it; replace it. This is especially true if the heat exchanger is old:

  1. Turn off power to the furnace and remove the front panel on the main chamber. 
  2. Find the heat exchanger. It sits between the blower assembly and the combustion chamber. 
  3. Look for signs of damage. Remove it if you find corrosion or other problems. 
  4. Replace the heat exchanger with a new one. Make sure the new one is compatible with your Carrier furnace. 


Problems with the condensate assembly, a damaged heat exchanger, a worn-out coupling, and issues with your humidifier can cause water to start leaking from your Carrier furnace. Thankfully, identifying and fixing the problem shouldn’t be too challenging, and it’s made even easier with the help of this guide.


  • Chris Hewitt

    Chris is a Texas-based freelance writer who loves the outdoors and working in his garage. When he's not enjoying the Texas sun, he can be found tinkering with all sorts of things in his workshop.

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