Which of the following is not a requirement for whirlpool bathtubs?

Non-potable water identification is not a requirement for whirlpool bathtubs because these tubs are typically designed to use potable water, supplied by the plumbing system in the home. The main concern with whirlpool bathtubs focuses on the safe operation of the system, which includes ensuring proper access to the pump for maintenance and serviceability, adhering to minimum air gap standards to prevent backflow contamination, and complying with specific flow rate measures indicated by GPM (gallons per minute) ratings for efficient operation. Non-potable water identification is more associated with systems like irrigation or certain industrial applications where water is not safe for human consumption, thus making it irrelevant for standard residential whirlpool tubs.