What is the required pipe size for more than three fixtures or a branch?

For a plumbing system, the required pipe size for more than three fixtures or a branch is determined based on the need to ensure adequate flow and pressure to all connected fixtures. When the demand on the system increases with multiple fixtures, a larger pipe size becomes necessary to accommodate the increased water flow without causing pressure drops or flow restrictions.

In this context, a 3/4" pipe is generally considered appropriate for the distribution of water from the main supply to multiple fixtures. It strikes a good balance, allowing sufficient volume and pressure for typical residential uses. Using a larger pipe size like 1" or 1 1/4" may be suitable for specific scenarios with excessive demand or longer distances, but for the average setup involving more than three fixtures, 3/4" provides the optimal solution to maintain both pressure and flow efficiency.

Thus, when designing or evaluating the plumbing system, adhering to the standard guidelines that recommend a 3/4" pipe for this scenario ensures functionality and compliance with plumbing codes.