What is the minimum diameter for the inspection pipe over both the inlet and outlet of a septic tank?

The minimum diameter for the inspection pipe over both the inlet and outlet of a septic tank is set at 18 inches. This dimension is essential for ensuring that maintenance workers can easily access and inspect the tank's inlet and outlet connections. An 18-inch diameter allows sufficient space for visual inspection, including the ability to check for blockages, assess the condition of the baffles, and perform maintenance tasks without obstruction.

Having this minimum size helps ensure safety and efficiency during inspections and repairs, as it provides adequate room to maneuver tools and access the necessary components of the septic system. Furthermore, this specification aligns with accepted plumbing practices and codes to ensure that systems remain functional and sanitary.

Larger diameters, while offering even more access, may not be necessary for standard inspections and can be more costly and cumbersome, which is why the 18-inch size is deemed sufficient and appropriate.