What is the minimum size of a fixture water supply pipe for a kitchen sink?

The minimum size of a fixture water supply pipe for a kitchen sink is 1/2". This size is appropriate because it provides sufficient flow and pressure to meet the demands of a typical kitchen sink, allowing for effective operation of faucets and any associated appliances like dishwashers.

Using a 1/2" pipe ensures that water can flow adequately to the fixture without significant pressure loss, which could lead to inadequate performance when multiple uses occur simultaneously. Plumbing codes and standards typically recommend this size to balance effective water delivery while accommodating standard fittings and connections commonly used in kitchen installations.

Larger sizes, such as 3/4" or 1", may be used in specific applications with higher demand but are not necessary for a single kitchen sink, leading to unnecessary material costs and complications in fittings. Conversely, smaller sizes like 3/8" are insufficient to meet the flow requirements of a kitchen sink, potentially leading to slow fill rates and diminished performance.