How to Unclog an Air Conditioner Drain Line

When a suspicious drip formed above our back door I knew it was again time to channel my "Tim the Toolman" skills and get to the bottom of it. Turns out what I initially thought to be a roof leak was something much more tricky--a clogged air conditioner drain line.

Gain Some Altitude

I suspected a problem with the air conditioner since when the drip started it had not rained in a few days. I checked the main air conditioner drain pipe which comes out of the side or our home and noticed it was draining, but not with as much volume as it typically did. In fact, a small puddle had formed in the past and I added a piece of 1″ PVC pipe to extend the drain away from our foundation. I accessed our attic via the garage and found the air conditioner's main evaporator unit.

The pan underneath the unit was nearly full of water, which I knew was a problem. The source of the drip was a secondary drain pipe connected near the top of the pan and running to the back of our house with an exit just above our back door. I was thankful the builder and air conditioner installer put the secondary drain's exit in a high-visibility spot so homeowners would know there was a problem.

Shop Vac to the Rescue!

I'd been wanting to pick up a small, inexpensive wet/dry vac for small garage spills, and fortunately a local home improvement store had one on sale. I picked up a Stinger-Vac (just a mini Shop Vac) for under $30 and returned home to put it to use. Lucky for me, the Stinger's hose attached perfectly to the 1″ PVC drain pipe and began to immediately suck out water and sludge that had accumulated inside the pipe. As it filled I simply dumped the water in our yard, reattached the vacuum and started it up again. After a few cycles I assumed I had made a dent in the amount of water from the pan and returned to the attic to view my progress. This time I carried a container of household bleach with me.

Preventive Maintenance

If I had taken this step earlier in the spring I could have probably avoided this near-disaster, but better late than never. I accessed the air conditioner's drain by removing a PVC cap on the top of drain pipe by hand. If the pipe was properly installed, this cap should only be tightened by hand and can easily be removed and replaced without any tools. I added a little bleach to the drain pipe to clear away any accumulated algae and mildew. Going forward, I will make this part of my checklist to prepare our home for summer.

My total material costs for the project was $32.09 for the Stinger Shop Vac. We had bleach on hand so I didn't factor this into the cost. The whole process took about an hour, and saved me from having to make a $50 service call to our air conditioner repairman. For a net savings of roughly $20 I am now the proud owner of a mini shop vac.