How to Fix a Clogged AC Drain Line

Clear a clogged AC drain line by locating the drain pipe, flushing it with water or vinegar, and using a wet/dry vacuum to remove stubborn blockages.

1. Kill Power First. Switch off your air conditioning unit at the thermostat and the circuit breaker. This prevents water damage and keeps you safe while working on the system.
2. Find Your Culprit. Find the AC drain line outside your home. It's typically a white PVC pipe coming from your indoor unit, ending near the outdoor condenser or foundation. You might see water dripping from it normally.
3. Confirm the Blockage. Remove the access panel near your indoor AC unit and locate the drain pan underneath the evaporator coil. If it's full of standing water, you've confirmed a clog. Empty the pan completely.
4. Flush It Through. Pour a cup of water slowly into the drain line access point near the indoor unit. If water backs up instead of flowing through, you have a clog. Try pouring water from the outdoor end of the pipe to push the blockage back toward the indoor unit.
5. Suck Out the Gunk. Attach the vacuum hose to the outdoor end of the drain line and create a tight seal with duct tape or a rag. Run the vacuum for 2-3 minutes to suck out the clog. You should hear debris being pulled through the line.
6. Kill the Algae. Mix equal parts white vinegar and water. Pour this solution slowly into the indoor drain line access point. Let it sit for 30 minutes, then flush with plain water. The vinegar dissolves algae and kills bacteria that cause clogs.
7. Confirm It Works. Turn your AC system back on and let it run for 30 minutes. Check that water flows freely from the outdoor drain line and no water accumulates in the indoor drain pan.