Thawing Frozen Drain - Pipes

Use a thermal imaging camera or infrared thermometer along the pipe run. The frozen section will be notably colder than adjacent pipe. Alternatively, run warm water into the drain for 30 seconds; if it backs up immediately, the plug is very close to the fixture. If it takes minutes to back up, the plug is farther downstream.

Once a pipe has frozen, the underlying vulnerability must be addressed: thawing frozen drain pipes