Clear a clogged condensate drain with a few simple steps.
Introduction
Clear a clogged condensate drain with a few simple steps.
If you notice water on the floor around your high-efficiency furnace, don’t panic. It could just be a clogged condensate line, a common problem caused by a buildup of sludge in the pipe. While it is not difficult to fix, a clogged condensate drain line can lead to water damage, rusted furnace parts and expensive repairs if left untreated. Fortunately, the process of unclogging a condensate drain line is relatively simple, with the right tools and some know-how. Ahead, find step-by-step instructions with input from Sebastian LaBier and Michelle Law of Blue Frog Plumbing and Drain.
What Is a Condensate Drain Line?
A condensate drain line is a pipe that carries away the moisture, or condensate, produced by a high-efficiency furnace to prevent water buildup and damage. Unlike traditional furnaces that expel exhaust gasses directly to the outside, high-efficiency models extract additional heat from the exhaust before venting it. As the gas cools within the system, it creates condensate that collects in a drain pan inside the furnace. This moisture is then channeled away through the condensate drain line to a floor drain, condensate pump or the outdoors.
What Causes a Furnace Drain to Fill With Water?
If the furnace’s drain is filled with water, it is either clogged, broken or improperly installed. A condensate line that is unclogged and pitched correctly will not fill with water but will instead carry it away to a drain, pump or the outdoors.
How Did My Condensate Drain Become Clogged?
The slow-moving water in a condensate drain contains minerals, debris and microorganisms. If enough time passes, this can lead to sludge or slime that can obstruct the pipe. “The condensate gets dirty because of the combustion by-products,” LaBier says, “and since the pipe is such a small diameter, it’s easy for it to get clogged.”
Tools Required
- Drain auger
- Wet-dry vacuum
Materials Required
- Clean water
- Duct tape
Project step-by-step (5)
Step 1
Shut off the furnace
To prevent the furnace from starting up while you’re working, shut it off first.
- Turn down the thermostat to its lowest temperature setting, or turn the switch to ‘off’ on the furnace electrical panel.
Step 2
Locate the condensate drain line
- Look at your furnace for a white PVC pipe, or a clear plastic tube, about 1 to 1.5-inch diameter. It should run from the furnace to a floor drain, condensate pump or to the outside of the home and may be routed through the floor or wall.
Step 3
Use a wet/dry vacuum
Use a wet/dry vacuum first to try to clear obstructions.
- Find the end of the condensate pipe at the outside of the house, at the floor drain or at the condensate pump.
- Place the wet/dry vacuum hose over the end of the pipe.
- If the hose is larger than the drain pipe, use tape to wrap around both to create an airtight seal.
- Turn on the vacuum and run it for a few minutes to remove any debris that may be clogging the line.
- For improved cleaning, add water at the service access point in the drain line while running the vacuum.
Step 4
Use a drain augerj
If the vacuum fails to dislodge the blockage, move on to a drain auger. This method will be most effective with condensate drain lines without many elbows, and should only be done with a hand auger. A power drain auger could break the pipe.
- Insert the tip of the drain auger into the end of the condensate drain pipe.
- Hold the drum steady and turn the auger handle clockwise to send wire into the line.
- If you meet resistance, turn the handle a few more times, hopefully capturing the blockage in the coiled auger tip.
- Turn the handle counter-clockwise to withdraw the auger wire from the pipe.
- Remove any debris on the auger tip and discard.
Step 5
Final rinse and finish up
- Pour water down into the pipe at the service access point or the drain trap to flush any remaining debris. This will also serve to prime the trap after vacuuming the line.
- Return the thermostat to a desired temperature or turn the switch to the “on” position to resume service.
FAQ
How do you prevent a clogged condensate drain line?
Regular maintenance of the furnace drain pan and condensate line will prevent clogs in the future. Consider using drain pan tablets to keep drain pans and condensate lines clear. These tablets break down slowly in the drain pan, releasing antifungal and antimicrobial agents that prevent any organic growth from developing in the condensate line. “Make sure to check your owner’s manual first,” Law says, “or you can void the warranty.” She also points out that some furnaces come with a condensate drain line brush that can be used for periodic maintenance cleaning.
Why does my condensate drain line keep clogging repeatedly?
If pitched incorrectly, the condensate drain line will not drain effectively. Water instead sits in the line and evaporates, causing repeated clogs. If you live in an area with hard water, that could also be the cause of frequent clogs. Law says to consider replacing lines that are difficult to clean or that clog regularly. “The parts are not expensive, and it’s not difficult to do,” she says.
About the Experts
- Michelle Law is an apprentice plumber at Blue Frog Plumbing and Drain, a full-service residential and commercial plumbing business in Springfield, Massachusetts.
- Sebastian LaBier is a Master Plumber at Blue Frog Plumbing and Drain, a full-service residential and commercial plumbing business in Springfield, Massachusetts.
