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How to Clean an AC Drain Line: 4 Different Ways

AC outdoor unit next to hedge - How to clean an AC drain line

Regularly cleaning the AC drain line is a task that homeowners rarely keep on top of and one that becomes a reason for many repair calls. Because of the lack of attention to preventative maintenance, it gives bacteria, mold, mildew and algae all that more time to grow and get a death grip on the pipes. That’s why it’s important to keep several tricks in your toolbox for when clogs get stubborn. Learn how to clean an AC drain line 4 different ways with Parts Town. 

How Do I Know If My AC Drain Line is Clogged?

There are usually some glaring signs that accompany a backed-up condensate line. However, a few of these symptoms can be mistaken for other problems, like a cracked drain pan, loose connections or an improper installation, so it’s important to run a full diagnostic before drawing any premature conclusions.

  • Water leaks – A telltale sign of a clogged air conditioner condensate line is coffee-colored stains that appear on the ceilings or walls. 
  • Drain pan overflows – With nowhere to go, condensation from the evaporator might fill up and overflow the drain pan, which leads us to our next bullet point.
  • Standing water around the unit – You might notice standing water around the unit or at the drain line’s access or exit points, depending on the location of the clog. 
  • High humidity levels – Since the condensation is not properly draining, you might notice high indoor humidity levels caused by the excess moisture. 
  • Musty or moldy smell – High indoor humidity levels create an ideal breeding ground for mold and mildew, contributing to an unpleasant, musty odor.  
  • AC stops cooling – Some AC systems boast a safety shutoff feature to prevent clogs from causing overflows and water damage.

How to Clean an AC Drain Line

There’s more than one way to skin a cat, and the same applies to cleaning AC drain lines. The easiest solution is to start with a commercial drain line cleaner, vinegar or bleach. However, if the blockage is more significant or it’s been a while since the last cleaning, it might make more sense to start with compressed air or a dry/wet shop vacuum. 

  • Step 1. Turn off the AC unit – Before anything else, turn off the air conditioning unit at the breaker box.
  • Step 2. Locate the AC drain line – Next, you’ll need to locate the AC drain line. The pipe is usually made of PVC or copper and runs from the indoor unit to the outside. Sometimes, the exit point might be pointed at a floor drain or sump pump inside the home, depending on the type of HVAC unit installed. 
  • Step 3. Access the drain line – Typically, you would find a t-shaped access point with a removable cap near the indoor unit. However, not all AC units are built the same, so sometimes that means you won’t be able to find an access point. In this case, you can pour the cleaning solutions directly into the drain pan.

With Bleach 

Bleach isn’t the best option if the line drains directly to the outside, as it can be harmful to the environment. When using bleach, be sure to wear the appropriate protective gear – face masks, goggles and gloves. Never mix bleach with any other household cleaners or chemicals. 

  • Step 4. Flush the line with bleach – First, you’ll want done your safety goggles before diluting one cup of bleach for every gallon of water. Then, using a funnel, pour the contents down the drain line. 
  • Step 5. Rinse the line with water – Let the bleach solution sit in the drain line for at least 30-60 minutes before flushing it out with warm water. This gives it ample time to kill and break up any mold, bacteria, algae or other organisms that have made themselves at home.
  • Step 6. Check for flow – After flushing the line with warm water, check the exit point for proper drainage. If the clog persists, you might try using a shop vacuum or an air compressor, which is explained in the sections below.
  • Step 7. Turn the unit back on – Once you’ve cleared the blockage, don’t forget to turn the AC back on!

With Vinegar 

Distilled white vinegar still gets the job done without the harsh fumes or potential health or environmental risks of other chemical cleaners, like bleach. Let’s learn how to clean an AC drain line with vinegar:

  • Step 4. Flush the line with vinegar – Use a funnel to pour a cup of distilled white vinegar into the drain line.
  • Step 5. Rinse the line with water – Let the white vinegar solution sit in the drain line for at least 30-60 minutes before flushing it out with warm water. This gives it ample time to kill and break up any mold, bacteria, algae or other organisms that have made themselves at home.
  • Step 6. Check for flow – After flushing the line with warm water, check the exit point for proper drainage. If the clog persists, you might try using a shop vacuum or an air compressor, which is explained in the sections below.
  • Step 7. Turn the unit back on – Once you’ve cleared the blockage, don’t forget to turn the AC back on!
AC drain line pointing toward floor - How to clean an AC drain line

With a Shop Vacuum 

A wet/dry vacuum is particularly helpful when unclogging even the toughest of jams, especially if you’ve got a bad case of dirt and algae buildup on your hands. Here’s how to clean an AC drain line with a shop vacuum: 

  • Step 4. Attach the vacuum to the exit point – First, you’ll want to create a seal between the shop vac and the drain pipe. Wrap a rag around the pipe before attaching the vacuum, or fasten it with duct tape. 
  • Step 5. Vacuum the drain line – Next, run the vacuum for a few minutes. If you see large chunks of debris or discolored water when you empty the vacuum, it’s a good sign that you’ve cleared the clog.
  • Step 6. Flush the line with water  – To verify, you’ll want to go back to the access point to flush the line with warm water to clear any remaining sludge.
  • Step 7. Check for flow – If the water flows freely out of the exit point, you’re good to go!
  • Step 8. Turn the unit back on – Don’t forget to flip the circuit breaker back on to restore power to your air conditioner!

With an Air Compressor 

Whereas shop vacs create areas of low pressure to clear stubborn clogs, air compressors deliver a blast of concentrated, high-pressure air that brushes and water just can’t touch. Let’s learn how to clean an AC drain line minus the hassle:

  • Step 4. Attach the air compressor to the access point – Attach the air compressor to the drain line access point. If there's gapping, you'll want to wrap it with a rag or duct tape to create a seal. 
  • Step 5. Clear the line – Run the air compressor in a few short-second bursts. It’s important not to use too much pressure at once in case the blockage is more severe.
  • Step 6. Flush the line with water – Once finished, flush the line with warm water.
  • Step 7. Check for flow – Is water freely flowing from the drain pipe? If not, go back and repeat the process. 
  • Step 8. Turn the unit back on – Once the clog is cleared, don’t forget to turn the power back on!

How Often Should I Flush My AC Drain Line?

The AC drain line should be cleaned out every one to three months to prevent buildup from mold, mildew, algae and dead bugs. This simple task only takes a few minutes and can end up saving hundreds or even thousands of dollars in repair.