How to Clean a Clogged AC Condensate Drain Line

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How to Clean a Clogged Condensate Drain Line

Last week our upstairs HVAC unit stopped working. My husband climbed up into the attic to troubleshoot, and quickly determined that we had a clogged condensate drain line.

That’s the line that your air conditioner uses to get rid of all the humidity that it pulls from the air. When everything is working properly, condensation runs down the drain line and exits outside your house.

But that drain line is pretty small, so it doesn’t take much for it to become clogged. Sediment, algae, mold and insects can all clog it up. When that happens, water backs up into the drain pan under your air handler. If you have a newer unit, a sensor will shut your unit off, alerting you to a problem. If you have an older unit, you may not know you have a problem, until the pan overflows and causes water damage to your home.

So how do you fix the problem? You could call an HVAC company to come clear the clog, but if you want to save money, this is definitely a problem that you can handle yourself.

Here’s What You Do:

1. Turn off your AC unit at the thermostat and at the breaker.

Condensate Drain Exit Point

2. Locate where the drain line exits your house, and make sure it isn’t clogged by an insect nest or something obvious. The exit point is usually (but not always) near the condenser unit. It’s possible that you may not have an outdoor exit point at all. Our upstairs HVAC unit runs to our bathroom drain.

Condensate Drain Line Access Point

3. If that doesn’t solve the problem, locate the drain line access point near your indoor air handler. Remove the plug. Then, attach the suction hose of a wet vac to the line, and try to suck the clog out. For this to work well, you need to make a tight connection between the hose and the line. We started by putting the vacuum hose over the drain line. That pulled some of the clog out, but it didn’t create enough suction to pull all of the clog out.

Sucking Out Condensate Drain with HVAC

So, we tried a Lint Lizard hose attachment that we had on hand. It’s intended for cleaning out dryer vents, but it worked perfectly for this. A Vaccuflex vacuum attachment would serve the same purpose, and is easier to find. What’s good about both of these is that they allow you to stick your hose in past the T, so that you’re sucking air/water from the condensate line, rather than from the air handler.

Clog from an AC Condensate Drain

Here’s the crud that we sucked out of our line on our fourth (and final) attempt.

4. If the drain line is still clogged, trying sucking the clog out from the exit point. It may just be further down the line than you’re able to reach from the access point.

Flush Condensate Drain with Vinegar

5. If, at this point, you still haven’t made any progress (or much progress), pour a cup of white vinegar into the access point, and allow it to sit for a few hours. This will kill any algae or mold that’s present, and help to break up the clog. Then, try sucking the line out again.

Be sure to place a bucket under the outdoor exit point before you add vinegar to the line. If it drips onto plants, it may kill them.

6. Still no luck? Then, you may want to try snaking out the line. You may not clean out your clog on the first attempt, but if you stick with it, you should be able unclog it without a call to an HVAC repairman.

How to Prevent Future Condensate Drain Clogs

Once we removed the clog, we flushed out the line with vinegar. I plan to make this a yearly maintenance task now. If you live somewhere humid, you may find that you need to do this more often.

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  1. WHERE were you when this happened to me a year ago?;) I TOO now make the vinegar flush part of my maintenance. My unit is 20 years old and while we are in Michigan and my semi-shaded brick house keeps the house cool in summer, I am babying it as long as I can…your help is SO timely for people. Thank you…now onto the surveys you have recommended to tuck some extra $ aside…

    1. Ha! If only mine had gotten clogged a year sooner 🙂 I figured there were probably lots of people like me out there, who didn’t want to pay for an HVAC service call, so figured I’d pass on the information.

  2. About 10 years ago my line clogged up and ruined the ceiling under where the pipe crossed. My AC man told me to pour 1 cup of Clorox in my drain pipe every year before I turn the AC on. Have never had a problem since I started doing it!

  3. So awesome. I just followed this tip with a vac to the pipe and it work. The sweet sound of my AC is back on. Thanks so much.

  4. I’m going to make it a habit to flush my drain with Vinegar every time I change my filter. I’ll even put a label inside my AC closet. I’m 64 and smart enough to know I don’t remember very well so I leave myself notes! Take Care.

  5. The above is exactly what needs to be done to unclog the condensate lines. I found that if you have a baby bottle cleaning wand, you can pour in the Clorox bleach and after a few hours suck out with the shop vac and use the wand taped to a snake or dowel and scrub out any remaining debris. Do it yearly prior to first use of the house A/C and have a worry free system. you will save hundreds of dollars believe me I know. I just spent $378.00 for a technician to do exactly these steps. “OUCH”!!!!!!!!!

  6. Wish I had check here first. Just paid $114 to get mine unclog left the big mess for me to get water out manually. Also hearing a hiss sound from it that I didn’t have before. Mine is inside near living room and wetted my carpet. I worked harder,longer to clean the mess he left than him unclogging. I feel cheated

    1. I just had the same thing happen to me a week ago. But heard it leaking at 12 midnight so we had to go through the night… In Florida… Without the ac. The next morning I poured vinegar and dish soap down the drain and used a wet vac to clear the clog. AC is back up and running with no issues. I will do this twice a year since I’m in Florida but vinegar will be a monthly treatment.

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