Is a single-compartment septic tank permitted if it is properly sized?

A single-compartment septic tank is typically not permitted, regardless of its size, because it does not adequately meet the requirements for proper waste treatment, especially for typical household wastewater. In most regulations, a septic system must include multiple compartments or stages to effectively separate solids from liquids and allow proper anaerobic digestion. Multi-compartment tanks enhance treatment efficiency by ensuring that solids settle and are broken down in a controlled manner.

While it may seem plausible that proper sizing of a single-compartment tank could be sufficient, the design and operational effectiveness of septic systems rely on more than just the tank's capacity. The complexity of typical household waste management necessitates the capabilities provided by multiple compartments. This helps in minimizing the potential for system failure and mitigating environmental risks related to untreated effluent.

The other options reflect variations that might apply in specific scenarios or areas, but the general rule is that a single-compartment tank does not align with modern septic system design standards, emphasizing the need for a multi-compartment approach to effectively manage and treat wastewater.