Final answer:
The IPC defines a 'fixture branch interval' as a group of fixtures in a plumbing system which can include various combinations of water closets, lavatories, bathtubs, showers, bidets, and floor drains.
Step-by-step explanation:
According to the International Plumbing Code (IPC), a fixture branch interval is a group of fixtures consisting of a water closet, lavatory, bathtub or shower, including or excluding a bidet, an emergency floor drain, or both.
The term fixture branch interval refers to the section of the plumbing system that serves a group of fixtures that branch from a stack, carrying waste to the building drain or building sewer. Understanding the IPC is crucial for ensuring that plumbing systems are designed and installed correctly, meeting both safety and hygiene standards.