Here’s a travel tip you won’t find in the airline safety briefing: Don’t drink the water.

For years, seasoned flyers have adhered to the “coffee pot” rule—never order a beverage that comes from a tank. Flight attendants know it. They won’t touch the stuff. Now, new research confirms our collective paranoia.

The study, released by the Center for Food as Medicine and Longevity, is enough to make you swear off in-flight tea forever. The center examined EPA records for 21 airlines from October 2022 through September 2025. Researchers calculated a water safety score for each carrier based on reported bacteria levels, safety violations, and how often they flushed their tanks.