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How to Clean a Clogged Air Conditioner Drain Line

How to Clean a Clogged Air Conditioner Drain Line

The AC drain line is crucial for your air conditioner’s performance. It helps to direct condensate from your HVAC to the outdoors. This, in turn, helps keep your AC running as it should. But over time, a build-up of form algae, mold, and even wet clumps of dust and dirt can clog up the drain line.

Keep reading to learn how to stop an AC drain line from clogging.

AC Drain Line Clogged Symptoms

If your A/C’s drain line is clogged, it can lead to problems. Dripping water can lead to other issues. Here are the main AC drainage line clogged symptoms;

Full drip pan

Even if you don’t see dripping water, check your A/C regularly for signs of a clogged AC drain pipe. Another common symptom is that the drip pan is often full or overflowing. This means the water isn’t draining as it’s supposed to, and there’s likely a clog. The same problem also applies to dehumidifiers.

Mold and mildew

If mold grows in your drip pan or around the unit, there may be more water there than usual, indicating a clog. Additionally, if you smell mold throughout the house, the smell likely originated at your A/C. And spread throughout your home via the ducts.

Water damage

There could be a leak if you find water spots or other signs of dampness near your A/C fan or on the floor around the unit. If you check regularly (once a month or so), you should hopefully be able to spot it before the water damage becomes a more serious issue.

Your AC is not working

Many newer air conditioners have a sensor that shuts down your system if it detects a backup of water. If your central air suddenly powers down, look for leaking water. You may have a clogged drainage line.

Water dripping around the inside unit

Another indication that it’s time for drainage line service is dripping or standing water near the furnace or evaporator unit. Check the area inside your utility closet or furnace room monthly for water leaks.

It’s easy to mistake water in a utility closet for an issue with your water heater rather than your HVAC system.

Your house feels unusually muggy

If you notice muggy air inside your home, it may mean a clogged drainage line. It can also mean a faulty pump but check for a clogged line. The relationship between humidity and the drainage line is possible algae growth inside the line.

Musty odors

When mold grows in the AC drip pan or anywhere near the AC unit, it’s a sign of more water than normal in the area. This often means you have a clog. Smelling mold in other areas of your home is often a result of a backed-up AC drainage line.

How to Clean AC Drain Line with Vinegar

You can prevent a clogged AC drain by performing routine cleaning. By pouring vinegar into your AC’s drain line, you will kill any mold, algae, mildew, and other forms of bacteria or fungi, preventing them from forming a build-up and causing a clog. Repeat this monthly for the best results.

Follow these steps to clean the clogged AC drain line with vinegar;

  • Turn off your air conditioner.
  • Turn the system off at the thermostat as well as at the breaker.
  • Locate your condensate drain line. Your drain line is a PVC pipe located near your outdoor unit and is attached to the wall of your house.
  • Identify the access point on the drain line. Most drain lines will have a T-shaped vent tee with a cover or cap.
  • Remove the cap at the top of the drain and inspect for blockage.
  • Add ¼ cup of distilled vinegar to the drain line through the opening where the cap was removed. Use regular distilled white vinegar, as the increased acidity boosts its cleaning properties.
  • Let the solution sit for 30 minutes.
  • Then flush the pipe out with water to ensure everything flows freely and operates as it should.

How to Clean an AC Drain Line with an Air Compressor

An air compressor is an excellent tool for clearing a clogged air conditioner drainage line.

Items needed

  • Air compressor
  • Tape
  • Plastic tumbler
  • Sponge


  1. Kill the power for the air conditioner where you will be blowing air through the drain line. You can find the cut-off switch for the AC unit in the main circuit breaker. Note: Some AC units may have a separate breaker box installed somewhere close to the condenser unit, sometimes located outside the house.
  2. Move the switch to the offsetting. Place a piece of tape over the switch, so it isn’t turned on while you are working.
  3. Locate the evaporator unit in your residence, where the drain pan is installed. This could be in an attic or basement. Pipes will connect the evaporator to the condenser unit outside your house. They are typically box-shaped units and will be installed next to the fan for your HVAC system.
  4. Find the location of the drain pipe in the drain pan.
  5. Remove the water in the drain pan if needed. This is especially important if you plan to be using an airline that can’t be used underwater. Instead, use a plastic tumbler to scoop up as much water as possible, then mop up the rest with a sponge.
  6. Insert the end of the air hose into the drainpipe opening and switch on the hose.
  7. Blow the air through the line until the clog has cleared or the line is running smoothly.
  8. Once the drain line is clear, use a funnel to slowly pour a gallon of white vinegar through the tube. This will help kill any remaining mold and algae and can help mitigate the risk of future clogging.

Where is my AC drain line? The pipe is usually connected to the side of the pan and then runs outside to drain the condensate. If the pan is filled with water, run your hand around the perimeter until you feel the drain opening.

Note: Refer to your user manual for specific instructions for using your air compressor or other methods for blowing air through the pipe.

How to Stop AC Drain Line from Clogging

Below are some tips and tricks you can use to prevent your drain line from clogging;

Regular flushing

Routine maintenance is an effective way to keep the line clean. The homeowner should regularly flush their lines with warm water. You may use bleach instead of water; unless your AC’s drain lines are made from PVC or ABS plastic. Bleach can break down both of those materials and the cement used to join fittings together. Vinegar is another option as it is an effective cleaner that will not damage pipes.

Install a proper drain line

In some cases, blockages may arise because the drain lines were not installed properly. For example, improperly sloped lines tend to be prone to clogs. As a result, it may be necessary to get an HVAC professional to re-route the line.

Install a condensate trap

A condensate trap with cleanout ports should be installed. Clogs will occur at the trap and will thus be easy to remove with a brush via the ports.

Use high-quality air filters

A quality air filter can ensure that dust does not build up on the evaporator coils. This dust is one of the main components of clogs. Therefore, the air filters must be changed every few weeks as dirty air filters will not be effective.

Clean your air filters often

Dust is one of the main causes of clogged air conditioner drains. Cleaning your AC’s air filters will prevent dust from building up on the evaporator coils. These filters should be cleaned every few weeks to prevent blockage and keep your air conditioner working at its fullest capacity.

Flush your drain lines

Routinely flushing your drain lines with warm water effectively prevents blockage and keeps your drain lines clean. However, for best results, use bleach instead of water, as it will kill any mold, mildew, or algae forming in your drain pipes. Vinegar is another option to kill mold, algae, and bacteria in your drain pipes that could cause clogs.

Check this too: How to Vent a Portable Air Conditioner Without a Window

Install a condensate trap

A condensate trap will prevent air from entering or escaping its pipes during operation. Blockage in the trap will also prevent pollution from entering the air handler and causing severe damage to your AC unit.

How Often Should You Clean Your AC Drain Line?

To keep your drain line clean, flush it with vinegar solution every three months. Then, to kill any harmful bacteria or build-up and make sure your system continues to operate at peak performance, clean your drain line every 30 days.