Sometimes the "drain" isn't frozen, but the vent pipe on your roof is clogged with ice/frost, creating a vacuum that prevents draining. Safely clearing the ice from the roof vent can often restore flow. 6. When to Call a Professional
Wrap the pipe in UL-approved heating tape. This provides a slow, consistent heat that safely thaws the line.
Salt lowers the freezing point of water, which can help melt ice even in hard-to-reach places.