How Clean Is Each U.S. Carrier's Tap Water?

Alaska Airlines and Allegiant carry the safest water among major U.S. carriers, according to analysis by researchers at Hunter College New York City Food Policy Center and DietDetective.com. An aircraft flies to numerous destinations and may pump drinking water into its tanks from various sources at domestic and international locations. The water quality onboard also depends on the safety of the equipment used to transfer the water, such as water cabinets, trucks, carts and hoses, the study said. Airlines are required to test samples from their water tanks for E. coli and for coliform bacteria, an E. coli indicator and must disinfect and flush each aircraft's water tank four times per year or test monthly and disinfect and flush once a year. Note that while flight attendants often distribute bottled water to passengers, coffee and tea often use water from the aircraft's galley.

The researchers ranked 10 major U.S. carriers and 13 regional ones by compliance with the Environmental Protection Agency's Aircraft Drinking Water Rule, which classifies passenger aircraft as public water systems and regulates water quality from lavatory and galley faucets. They retrieved data Aug. 15 from the EPA's Aircraft Reporting and Compliance System database analyzing nine categories: galley water that was positive for E. coli, galley water that was positive for other coliform bacteria, lavatory water that was positive for E. coli, lavatory water that was positive for other coliform bacteria, number of ADWR violations, number of open pre-2019 ADWR violations, timeliness in reporting sample data to the EPA, failure to conduct routine monitoring and failure to perform corrective actions as required. In addition, researchers surveyed the major carriers.

The study found fewer ADWR violations than in 2012, the first full year the EPA rule was in effect. For major airlines, violations have decreased 69 percent, falling from 262 to 81, while violations among regional airlines have decreased 71 percent, falling from 351 to 103. The authors said the declines could owe to weaker enforcement by the EPA, which has issued few penalties in recent years. However, the study did not rule out that carriers have improved the quality of water flowing through their sinks.