Does the lavatory flush use blue juice, or what fluid is used normally?

• A. Yes, blue juice is used
• B. No, it uses fresh water from the potable water system; bluewater can be used during servicing
• C. Only during service; uses blue juice otherwise
• D. It uses gray water

Answer: (B)

The lavatory flush uses potable water from the aircraft’s drinking-water system. This keeps the flushing fluid clean and safe for regular operation. During servicing, a colored service fluid sometimes called bluewater may be used for testing or maintenance tasks, but it is not used for normal operation. Gray water refers to the waste that has left the bowl, not the flushing fluid. So the normal flush is fresh water from the potable system, with bluewater only used during servicing.