How to Unclog AC Drain Line

How to Unclog AC Drain Line

In addition to cooling the air inside your home, your air conditioner removes humidity from the air. This dehumidification process collects water vapor from the air inside your home and sends it outside through a drain line attached to your AC.

Your AC drain line needs to be free of obstruction to allow your AC system to properly function. However, your air conditioner’s drain line is wet and dark, making it an ideal home for algae, mold, and other bacteria growth. Over time, the buildup of bacteria causes your AC drain line to drain more slowly and eventually clog.

How do I know if my AC drain line is clogged?

The most noticeable signs of a clogged AC drain line include the following:

If your AC drain line becomes clogged, condensation from the standing water may leak from the pipes, causing water damage and a musty smell in your home. As the clog worsens, the standing water starts to accumulate inside the drip pan. If the water level inside the pan reaches a certain height, a safety sensor switch called a float switch will turn your air conditioning system off. This prevents water from overflowing from the top of the pan and causing damage to your AC system. Your AC will not turn back on until the water drains.

How to Unclog Your AC Drain Line in 6 Steps

If you notice water leaking or accumulating in the drip pan, you can try to perform some DIY AC maintenance. Unclogging and cleaning your AC drain line is easy to do and can be done using just a few household items. Here’s how to unclog your AC drain line in 6 steps.


  • Garden hose
  • Wet/dry vacuum (optional)
  • Duct tape (optional)
  • Vinegar


Step 1. Turn off your air conditioner

Before starting, turn off your AC system at the thermostat and the breaker or disconnect/shut-off box to be safe. This helps protect both you and your AC system.

Step 2. Locate the drain line

Your AC drain line is a white, T-shaped PVC pipe that is generally located inside a utility closet, your garage, or the attic. Depending on your AC system, it might be hidden by a removable access panel. Follow the PVC pipe and find where the drain line exits your home and ensure that it is not obstructed by dirt or other debris. If you can’t follow the drain line, try looking near the AC condenser, which is the outdoor component of your AC system.

Step 3. Use a wet/dry vacuum to remove the clog

If you don’t have a wet/dry vacuum, skip to the next step. If you do have a wet/dry vacuum, you can try removing the clog by attaching the wet/dry vacuum to the end of the AC drain line. Turn on the vacuum for about a minute to suck out the clog and excess water in the line. For most clogged drain lines, this is all you’ll need to do to unclog your AC drain line, but you’ll want to follow the next few steps to completely clear out your AC drain line.

Step 4. Use a garden hose to clear the drain line

Find the point of access on your drain line, this is generally a T-shaped piece with a cap on it. Remove the cap and wedge the hose into the drain pipe.

IMPORTANT: Make sure the water flows down the drain line, not back into your AC system. You may need to use a different access point or find a way to block off the water flow to your AC system. Once the hose is securely in the drain line, turn on the water for a few seconds and make sure that the water flows down the drain and it’s not leaking all over the place. If water is leaking, try resecuring the hose with duct tape. Once you’re sure the hose is secure, turn the water on to the max flow rate and let the water clear your drain line. Once the water coming out of the drain line is clear, turn off the hose.

Step 5. Clean your AC drain line

After the clog is cleared, clean your AC drain line by pouring a cup or more of vinegar down the drain. The vinegar will help to kill the algae, mold, and other bacteria that can build up and cause clogs. Repeat this process monthly to keep your condensate drain free of clogs.

Step 6. Replace the cap and turn your AC system back on

Don’t forget to place the cap back on your AC drain line and turn your AC system back on at the breaker or disconnect/shut-off box, and then at the thermostat.

How to Prevent Future AC Drain Line Clogs

Keeping the drain line as clean as possible should be part of your regular AC maintenance routine. You’ll want to flush your AC drain line with vinegar monthly to eliminate any algae, mold, or other bacteria or sludge buildup in your AC drain line and prevent your drain line from clogging up.

2 Replies to “How to Unclog AC Drain Line”

  1. If using a wet/dry vac at the end of the condensate line would it be advisable to block the line at the a/c unit inside the house to create a strong suction? Otherwise, it seems that a lot of air would be sucked through the line reducing the effect on the clog. Thanks.

  2. No Ed you need to keep the line open inside the house so air can be sucked through to the outside of the house along with whatever is clogging up the pipe

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