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Why is My AC Drain Clogged and How Do I Fix It?

Whether you came home to an unexpected pool of water under your air conditioner or just realized that the familiar drip, drip, drip of your outside condensation line has suddenly stopped, it’s no fun to discover a clogged air conditioner drain.  Luckily, it’s a common problem that can be easily taken care of by a careful homeowner.

What Causes A/C Drain Line Clogs?

The nature of A/C drain lines is also their worst enemy.  Since they drain steadily for only part of the year, they aren’t constantly flushing out dust and debris.  When the weather cools down and the A/C runs minimally or not at all, dust, algae, bacteria and random gunk collect in this tube and set up shop.  You might not notice at first, since you’re barely using your air conditioner, but after some hot days you may have a very wet floor, basement or crawlspace due to the build-up. I’ve seen a drain line leak for months and ruin one of our tuft and needle mattresses.

Although it’s annoying for you, and not great for your floor or your air handler, the miniature creatures and plants trying to live in your condensation drain line aren’t harmful, making this a perfect DIY project.  In fact, cleaning your drain line and keeping it clean should be on the “to do” list of every homeowner with an air conditioner.

Cleaning the Air Conditioner Drain

There are several different ways to clean a clogged drain line because not all drain lines are created equally.  Before you get near your drain line to clean it, though, you need to keep in mind that PVC drain lines with lots of connections can be very delicate and bust easily, so no use of brute force to move that clog along.  Since they’re so small, you can’t use a plunger either, so what can you do?

Short drain lines are often cleaned out with nothing more than a long, soft brush — the bristles can be used to snag the material causing the clog.  You’ll then pull it out or push it forward, as the situation dictates.  Longer runs can be tackled with a smaller piece of plastic tubing fed into the line like a drain snake.  This is useful for straight runs, but if there are bends, you’ll run into trouble.

If you’re a truly handy person, you can build a vacuum for your condensate line using the shop vac you already own.  There are products on the market, like the DIYVac that can be used for some types of drain lines, but if your drain line is soft plastic or simply a different size, you can still create a PVC fitting to slip into or over your existing drain line.  

The hardest part is creating the connection, then all you need to do is flip your shop vac to its suction setting.  Leave your vacuum sucking for up to about five minutes.  When you take the lid off, you’ll have the clog and everything that it was holding back.  Gross, but effective.

Maintaining a Clean Drain Line

Once you get the muck out of your drain line, you can prevent clogs like that from forming again by sticking to a maintenance schedule.  If your drain line doesn’t already have a clean-out, it’s a good idea to install one to make this process easier.  For a soft plastic drain hose, it may be easier to take the hose off at the furnace for cleaning.

With your chosen access point open, use a funnel to pour up to about a cup of bleach or vinegar into the line, running away from your air handler.  Let that liquid come all the way out of the line before following it with as much water to flush the harsher chemicals out.  Repeat this once a year, just as air conditioning season starts, and you’ll never have to worry about A/C drain clogs again.


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