The invert of the first relief line must be at least how many inches lower than the invert of the septic tank outlet?

The requirement that the invert of the first relief line must be at least 1 inch lower than the invert of the septic tank outlet is based on ensuring proper drainage and preventing backflow in the septic system. This 1-inch difference allows for sufficient gravity flow, which is essential for the effective operation of the system. This distance helps mitigate the risk of solids entering the distribution lines and ensures that wastewater flows smoothly from the septic tank into the drain field without causing blockages.

Maintaining this specific distance is crucial for the overall functionality and longevity of the septic system, as any deviations could lead to operational issues. Therefore, adhering to this standard helps uphold the integrity of the septic installation and protects both the system and the surrounding environment.