What is the minimum size of a fixture water supply pipe for a hose bibb?

The minimum size of a fixture water supply pipe for a hose bibb is typically 1/2 inch. This size is generally adequate to provide a sufficient flow of water to satisfy the demands of a standard hose bibb application. A 1/2-inch pipe can handle most residential hose bibb needs, including connecting to garden hoses and sprinklers, without significant pressure drop or flow restriction.

The choice of 1/2 inch also aligns with common plumbing practices and codes, which aim for an effective balance between adequate water supply and manageable pipe sizes for installation and cost considerations. Larger diameters, such as 3/4 inch or 1 inch, would provide more flow but are generally not necessary for typical hose bibb use and might lead to unnecessary material expenses and installation complexities.