The line is likely clogged if it doesn't drain. To resolve, flush the line with a vinegar-water solution or use a wet/dry vacuum to remove debris. This Nu Calgon AC Drain Line Cleaner from Amazon ...

A clogged drain line can cause leaks and mold growth. Locate the drain line (usually a PVC pipe), use a wet/dry vacuum or ...

Using only one household item, HomeTips4You shows how to "Clear out all the gunk and the funk within that AC drain line" ...