Which fixture typically requires the largest minimum water supply pipe size?

The flush-valve toilet typically requires the largest minimum water supply pipe size among the listed fixtures due to its design and operational requirements. Flush-valve toilets utilize a large valve that allows for a greater volume of water to flow rapidly during each flush. This necessitates a larger pipe size to ensure adequate water delivery to generate sufficient flushing pressure and volume effectively.

The water supply size is crucial to maintain optimal performance, as insufficient supply can lead to poor flushing efficiency, repeated clogs, and potential hygiene issues. Therefore, plumbing codes often specify larger supply lines for flush-valve toilets compared to other fixtures, such as flush-tank urinals, sillcocks, and bidets, which generally function effectively with smaller pipe sizes.

This distinction is important for plumbing contractors to understand, as ensuring the correct pipe size during installation can greatly influence the performance and reliability of the plumbing system.