What is the minimum size of a fixture water supply pipe for a flush-valve toilet?

The minimum size of a fixture water supply pipe for a flush-valve toilet is 1 inch. This specification is based on the requirements for providing adequate water flow and maintaining proper pressure for flush-valve toilets, which typically have a higher demand for water compared to standard tank-style toilets.

Flush-valve toilets rely on the rapid influx of water to ensure a powerful flush, and utilizing a larger supply pipe ensures that the toilet receives enough water quickly during operation. A 1-inch supply pipe can accommodate the high volume of water needed without experiencing significant pressure drops that could lead to inadequate flushing performance.

In contrast, smaller pipe sizes such as 1/2 inch, 3/4 inch, and 3/8 inch are typically insufficient for this application, as they may not deliver the necessary water volume and pressure in a timely manner, compromising the functionality of the flush-valve system. Therefore, selecting a 1-inch pipe for a flush-valve toilet is critical for optimal performance.