Guides ยท Updated 2026-11-13
How do I flush my AC drain line?
Quick answer: Turn the AC off, find the drain line access cap near the indoor unit, pour in about a quarter cup of distilled white vinegar, wait 30 minutes, then flush with water.
Step by step
- Turn the thermostat to Off.
- Find the PVC drain line near your indoor unit (often in the attic or a closet). Look for a T shaped fitting with a cap.
- Remove the cap and pour in about a quarter cup of distilled white vinegar.
- Wait about 30 minutes, then pour in water to flush it through.
- Put the cap back and turn the AC on. Check that water drips outside where the line ends.
The Home Maintenance Minute
If water is sitting in the pan under your indoor unit, the drain line is likely clogged. Flush it before it overflows into the ceiling.
If water is sitting in the pan under your indoor unit, the drain line is likely clogged. Flush it before it overflows into the ceiling.
When to call a pro
Call a licensed HVAC technician if the line stays clogged, the pan keeps filling, or the system shuts itself off.
By The Home Keeper Team. General information only, not a substitute for a licensed pro.