All interior supply plumbing pipes must be at least what diameter?

The requirement for all interior supply plumbing pipes to have a minimum diameter of 1/2" is based on standards that ensure adequate water flow and pressure throughout the plumbing system. This size is generally sufficient to provide enough volume for typical household demands, ensuring that fixtures such as faucets, showers, and appliances receive the necessary water supply without significant pressure loss.

Using smaller diameter pipes, like 1/4", may lead to inadequate water flow, which could create problems with low pressure in various fixtures and slower filling times for appliances. While larger pipes such as 3/4" or 1" can be beneficial in certain situations for increased flow or when servicing multiple fixtures, the baseline requirement is set at 1/2" to balance efficiency with performance in typical residential plumbing applications.