How many inches lower should the outlet invert of a septic tank be compared to the inlet invert?

The correct answer is that the outlet invert of a septic tank should be 3 inches lower than the inlet invert. This specific elevation difference is crucial for the proper functionality of the septic system.

The downward slope from the inlet to the outlet ensures that wastewater flows freely through the system, preventing any potential backup or stagnation that can lead to treatment inefficiencies. This gradient assists in maintaining the desired hydraulic flow and encourages the separation processes to occur effectively within the tank. Additionally, this configuration helps avoid the risk of scum blockages at the outlet, which can disrupt the flow of effluent.

Understanding this dimensional requirement is essential for maintaining the health and efficacy of a septic system, and ensuring compliance with local regulations and standards for septic installations.