What feature is essential for the wall between compartments regarding its fitting?

A tight fitting for the wall between compartments is essential because it serves to prevent the mixing of wastewater from different sections of the septic system. In a multi-compartment tank, each compartment's function is vital for proper treatment and separation of solids and liquids. A snug fit ensures that contaminants do not escape into adjacent compartments, which could compromise treatment efficiency and public health.

Moreover, tight fittings help to minimize odors and reduce the risk of leakage, which might otherwise allow untreated effluent to escape into the environment. This is particularly important in maintaining the integrity and performance of the septic system, ensuring long-term functionality and compliance with health regulations.

A loose fitting could lead to issues like cross-contamination and ineffective treatment, while adjustable or removable fittings may not provide the necessary permanence and integrity needed for long-term sewage management. Therefore, a tight fitting is the optimal choice for maintaining the separation and effectiveness of each compartment in a septic tank system.