What is the smallest permissible size for a building sewer?

The smallest permissible size for a building sewer is 1 1/4". This size is critical because it ensures that the sewer can adequately accommodate the flow of wastewater from a building without experiencing significant risk of blockage or insufficient drainage capacity.

Building sewers are designed to handle the drainage from plumbing fixtures, and smaller diameters, such as 1" or even 1 1/2", may not provide sufficient capacity, especially during peak usage times. By adhering to the minimum size of 1 1/4", the system can maintain proper flow rates, reducing the likelihood of backflow or maintenance issues.

It's important to ensure that sewer lines are not only compliant with building codes but also function effectively under various loading conditions, which is why this specific size is recognized as the minimum standard. This consideration helps safeguard against plumbing problems that can arise from inadequate sizing of sewer lines.