Why does my AC drain line keep backing up and leaking?
AC drain lines frequently clog within a few weeks, causing the unit to drip water underneath and trigger leak sensors. Even after clearing the clog, the system will continue to leak if there is an issue with the cap on the access point.
What people tried
Every workaround mentioned in the threads below. We haven’t tested any of them — and nobody here is claiming they worked.
Found another way around this?
Share your steps and trade-offs so fellow engineers don't have to reinvent the wheel. No account required.
- 1Using a shop vac to try and clear the years of muck from the line.Did this help you?
- 2Replumbing the line to add an access point for pouring vinegar to rinse it.Did this help you?
- 3Leaving the cap off the access point to break the vacuum.Did this help you?
- 4Installing a P-trap close to the outlet from the coil.Did this help you?
- 5Manually starting and stopping the appliance to allow the water enough time to drain slowly.Did this help you?
In their words
Unedited, grouped by where they were said, most upvoted first within each place, each linked to the thread it came from.
“within a couple of weeks, the line fully clogged and my unit started dripping water underneath.”source ↗
“My water sensor went off last week, notifying me of a small leak. Sure enough, the line had clogged again but we were able to clear it.”source ↗
“To our surprise, a small leak continued. Called our HVAC guy back out. He took one look and said that the problem was the cap on the access point.”source ↗
Where this came up
People with this problem also raised
- 2Why does my refrigerator ice maker fill tube keep freezing?
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- 15Why is water backing up into the sink when appliances drain?
- 16What is this extra pipe dripping into my sink drain?
- 2Why does coolant overflow from the reservoir and not return?
- 5Water leaking behind new gutters and soffits