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How to Clean & Prevent Clogged Condensate Drain Line | Leaking AC

by vscontent on July 3, 2016

how to prevent and unclog condensate drain line

If your air conditioning system is leaking water, it’s probably the result of a clogged A/C condensate drain line. If not, then you may have a crack in your drain pan or your clogged air filter is causing frozen evaporator coils that are leaking.

How to Inspect and Clean Evaporator Coil

It’s simple to tell if your evaporator coils are frozen – simply open up the cabinet of your indoor air handler and check. If you notice frozen evaporator coils, turn off power to your A/C unit at the thermostat and turn your fan setting to “on.”

To fix the issue, it may be as simple as replacing your air filter (clogged air filters restrict the necessary airflow for evaporator coils).

After you have replaced the air filter, wait until the evaporator coils are no longer frozen to turn the unit back on. If the air filter doesn’t fix the issue, you may need to call a professional to address refrigerant or other problems.

It’s also important to keep your evaporator clean because the condensate that drips down goes straight into your drain pan and condensate drain line. If your coils are dirty, water and debris will fall into your drain pan, potentially causing a clog. Learn more about evaporator coils and how to clean them here.

Scheduling annual air conditioning maintenance includes a full cleaning of your evaporator coils and indoor air handler. If your evaporator coils are frozen, give us a call at 253.292.3995.

How to Repair Cracked A/C Drain Pan

Another cause of a leaking air conditioner is a cracked drain pan. This is also very easy to check. Simply grab a flashlight and check your drain pan for any cracks, holes, or other leaks. Your drain pan is located underneath the evaporator coils. Although small cracks can be fixed with epoxy glue, serious cracks require a full replacement.

If you have a central air conditioning system, you may have noticed a drain pan in your indoor unit that drains water to an outdoor drain line.

This drain pan and line makes sure that the dripping condensation from the indoor air handler and coils can properly drain outside. If it is clogged, then water can buildup in the drain pan and cause water damage inside the home.

To seal the cracks in your drain pan, first turn off power to your A/C unit at the breaker box. Then, remove the drain pan, suck out all the water with a wet-dry vac, and clean it thoroughly. After the drain pan is completely dry, you can use your water-based sealant to fix the cause of your A/C leak. Click here for more tips on repairing your A/C drain pan.

How to Keep A/C Condensate Drain Line Clean and Clear


The most common cause of air conditioning leaks are clogged A/C drain lines and the most common cause of drain line clogs is mold and algae buildup.

Luckily, it takes a long time for a clog to develop and it can be easily prevented by pouring some vinegar in the line every three months. Since many indoor air handlers are located in a hot attic, many homeowners choose to conduct this maintenance chore in the early mornings or late evenings.

The pipe in the attic or basement that leads away from the drain pan usually includes a tee with a threaded plug that is easy to open. The best way to kill the algae growth is with a dose of ordinary white vinegar that is a staple in most kitchens. The technique involves removing the plug and slowly pouring six ounces of vinegar into it

  1. Locate your indoor condensate drain line
  2. Find the drain line that leads away from the drain pan.
  3. Unscrew the pipe cap at the end of the “T” and pour 6 ounces of vinegar (about 3/4 of a cup) down the opening.

You may have also read that bleach can be used. Although bleach is a great way to clean and prevent mold and algae, it can also create problems in your drain line. Vinegar does the same thing – kills algae and mold – but doesn’t risk any damage or corrosion to your drain lines.

How to Clear Clogged Condensate Drain Line

First try pouring vinegar down your clogged condensate drain line as described above. Wait a day to see if the clog has been removed. If you still have a clog, you may have to call a professional to unclog it or try this DIY method, which involves a wet-dry vac.

You can also try using this A/C Drain Sucker, although we have no knowledge of whether this will get the job done or not.


For a thorough how-guide on using a shop vac to clear your condensate drain line, read this Energy Vanguard article. The easiest way to ensure that all the crud from inside your drain line is removed, is to check if your HVAC contractor includes this service as part of their annual A/C maintenance tune-up. Make sure your contractor includes A/C drain line clearings before you schedule the job.

Additional moisture control and air conditioning tips for the home:

One of the best ways to prevent mold and mildew in your home is to have a professional air quality expert examine your home. Removing mold is only a temporary solution if the primary cause hasn’t been addressed. Call Pacific Air Systems at 253.292.3995 to speak with one of our Comfort Specialists.

Since 1984, we’ve been proudly serving our communities in Federal Way, Graham, Spanaway, University Place, Steilacoom, Sumner, Lakewood, Puyallup, Tacoma and Gig Harbor. We are known in the Tacoma/Lakewood area for professionalduct sealing and cleaning solutions.

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