By design, AC units remove moisure from the home, condenses it, and drains it from the home. The average central AC unit drains 2 to 4 gallons of water per day. The moisture pulled from the home passes over a coil, called the A-coil because of its slanted shape. It’s shape guides water into a pan. The pan is connected to a drain that removes the water from the unit and from the home. A joke among HVAC contractors is that “There are two types of drain lines: those that have clogged and those that will clog.”
At some point, if not maintained, the drain line will get plugged and cause a leak. These clogs are typically made up of dust, debris, and sometimes algae or mold growing in the moist environment. Combined, it is called sludge. It will slow down or prevent the flow of water, eventually causing a leak. Although messy, cleaning out a clogged condensate drain is a simple DYI project for a willing homeowner.
NOTE: Before beginning, use the breaker box to cut power from the HVAC unit to prevent electrical shock. This is different than cutting power off at the furnace, please use the breaker!
Here’s how to do it:
- Find the drain line. It’s usually a ¾-inch PVC pipe coming out of the bottom of the drain pain.
- Remove the sludge from the pipe with a wet/dry vacuum. Put the end of the hose right into or over the drain pipe. The success rate of this technique is more than 80 percent.
- If the shop vac doesn’t work, try to remove the furnace cover and suck out debris and dirt from the pan. This should probably be done anyway to prevent accumulated sludge from making its way into the drain.
- Once you have found the pan, use a paint scraper to remove hardened sludge and then vacuum it away.
- For clogs that just won’t give, which are rare, try using an air compressor to force out the clog.
- Be sure to clear the drain pan and drain the line once a year to remove sludge and prevent leaks from happening in the first place.
If none of these methods work, there may be a hole in the drain pain. These pans can corrode and rust through over time. It’s not necessarily common, but it does happen. If you find a hole or holes in the drain pain, purchase a quality, water-resistant patching material to repair the drain pan. If all else fails, replace the drain pan or contact your trusted HVAC contractor for a service call. Many people are surprised to learn that this is a DIY project. If you have the right tools and the confidence, then save the money and attempt to clear the clog yourself. Don’t forget to cut the power from the breaker box. Good luck!