Updated: Nov 20
In this article, we go over 10 methods to clean out condensate drain lines and traps on air conditioning systems! The condensate drain line is responsible for removing the water that is extracted from the indoor air (humidity) during air conditioning mode. Over time, the drain trap and/or line can become clogged with dirt, dust, bio-growth, and other debris. When this happens, the water may back up into the system, overflowing out of the primary drain pan and causing damage to the system and/or building.
Let's discuss the fastest methods for clearing these lines/traps. To prepare for cleaning, the system's power must first be switched off so that air is not being pushed or pulled through the drain line/trap. Also, if you have access to the trap, remember to fill it back up with water when you are done and cap off any service access openings when complete.
Method #1: Using a Shop Vac to Evacuate The Drain Line at the Outside Location
Simply connect the wet/dry vacuum hose to the end of the drain line outside and turn on the vacuum. The suction will help remove any blockages or debris in the line. To better clean out the lines, add water at the indoor unit primary pan or the line's service access location while doing this!
Method #2: Blowing out the Condensate Line with 30 PSI of Compressed Air using an Extended Tip.
To get a better seal inside the tubing, wrap the end of the extended tip with electrical tape. Then, place the tip down into the trap and apply the compressed air to blow out the debris. Make sure to not apply excessive pressure because this could cause a pipe joint to separate and leak. When finished, fill the trap back up with water and replace the cap.
Method #3: Clear the Trap Using a Brush
Remove the caps on both ends of the condensate trap. Pull the brush through the trap to break up clogs and extract debris. When finished, fill the trap back up with water and replace the caps.
Method #4: Clearing The Drain Line at a Horizontal Tee With A Shop Vacuum
When there is a horizontal access tee, use a 1/2" CPVC 90° fitting with a section of CPVC pipe attached to a 3/4" PVC bushing, to access the inner pipe. The 3/4" bushing typically fits into the shop vac's hose end. This assembly can be used to blow or suck out debris inside the horizontal section of pipe. Remember to fill the trap with water and replace any service caps when complete.
Method #5: Vacuum the Trap Using a Shop Vac Hose with a Section of CPVC Pipe Attached to the End.
Simply connect the 3/4" to 1/2" pipe to the end of the shop vac and insert it into the condensate trap. Remember, attaching electrical tape to increase the diameter of the 1/2" CPVC pipe will allow it to seal better when inserted into the trap. Turn on the shop vac. Remember to fill the trap with water and replace the service caps when complete.
Method #6: Blow Out the Condensate Trap Using the Shop Vacuum
A shop vac can be used to blow out the trap instead of sucking out the debris. In this scenario, move the vacuum hose end to the outlet of the shop vac instead of at the inlet. Then insert the 1/2" CPVC pipe into the trap and turn on the vacuum. Remember to fill the trap with water and replace the service caps when complete.
Method #7: Blowing Out a Condensate Trap With Clear Vinyl Tubing Only In the absence of an accessible electrical outlet or pressurization device, you can use a clear vinyl tube with electrical tape on the end inserted into the trap. At the exposed open end of the clear vinyl tube, apply force through the tubing with a large breath.
Method #8: Applying 30 PSI of Nitrogen Through a Cone End to Blow Out The Condensate Trap.
A nitrogen tank can act as an alternative to compressed air. Attach a hose and air gun to the nitrogen regulator and set the secondary regulator to 30 PSI. Apply the air gun end to the open section of pipe and allow the nitrogen to blow out the clog. When finished, fill the trap back up with water and replace the cap.
Method #9: Applying 30 PSI of Nitrogen Through an Extension Tube to Blow Out the Condensate Trap.
Attach a hose and air gun to the nitrogen regulator and set the secondary regulator to 30 PSI. Add the extension tube with electrical tape on the end to the air gun. Put the extension tube down into the trap and allow the nitrogen to blow out the clog. When finished, fill the trap back up with water and replace the cap.
Method #10: Using Pressurized Air Through a Flexible Extension Hose
To get to hard to reach places, a small flexible extension hose can be added to the air gun. Fish the flexible hose end (poly tube end) into the open section of the condensate drain line. Cover the remainder of the opening and then apply the air/nitrogen pressure through the drain line. This method can be used when there is no service access cap or when the only access is the primary drain pan outlet.
A Quick Note: Method #1 is a preferred method because not only is the clog removed, but the entire drain line can be flushed by adding water into the indoor service access cap or drain pan. Always add water back into the trap when complete! This stops any air from being pulled or pushed through the drain line and allows water accumulating in the primary pan to drain out properly.
Want to see these methods in action? Check out our YouTube Short! https://youtube.com/shorts/MkHgXlt9p8M Learn more about the function of the condensate trap by watching our videos below! Check out our free Quizzes to test your knowledge here! Check out our Free Calculators here! If you want to learn about refrigerants and how they work in a system, check out our “Refrigerant Charging and Service Procedures for Air Conditioning” book . Test your knowledge with our 1,000 question workbook along with the answer key! We also have quick reference cards for use out in the field! Bundle Packs are a great way to save and get faster shipping! Check out www.acservicetech.com/store Tools that we use: www.amazon.com/shop/acservicetechFollow us on Facebook for Quick Tips and Updates here!
Published: 5/10/23 Author: Craig Migliaccio
About the Author: Craig is the owner of AC Service Tech LLC and the Author of the book “Refrigerant Charging and Service Procedures for Air Conditioning”. Craig is a licensed Teacher of HVACR, Sheet Metal, and Building Maintenance in the State of New Jersey of the USA. He is also an HVACR Contracting Business owner of 17 years and holds an NJ HVACR Master License. Craig creates educational HVACR articles and videos which are posted at https://www.acservicetech.com & https://www.youtube.com/acservicetechchannel