A house sewer shall be laid on a grade of not less than ______ inches per foot.

The minimum grade for a house sewer is established to ensure proper drainage and to prevent the accumulation of sewage, which can lead to clogs and backups in the system. A grade of 1/8 inch per foot provides a balance between ensuring adequate flow and preventing excessive velocity that could lead to erosion of the pipe material or displacement of the line.

When the sewer line is laid at this minimum grade, it allows for the effective transport of wastewater by utilizing gravity, which is essential in maintaining the functionality of the residential plumbing system. This grade is commonly accepted and referenced in plumbing codes, providing a standard for installers to follow for optimal performance.

Grades such as 1/4 inch per foot might be too steep for some conditions, while grades of 1/3 or 1/10 inch per foot may be insufficient for effective drainage. Therefore, the specified grade of 1/8 inch per foot is critical for ensuring that any solids within the sewage flow are adequately carried away without settling in the pipes.