The treatment capacity for all septic tanks shall be sized for which volume?

The treatment capacity for all septic tanks is sized based on the daily (24-hour) peak volume of the facility being served. This approach ensures that the septic system can handle the maximum amount of waste generated during the busiest periods, which is essential for maintaining the functionality of the system and preventing overloading. By sizing the septic tank for the daily peak volume, it can effectively manage fluctuations in water usage, such as increased flow from multiple activities occurring within a single day or weekend.

Using the daily peak volume as a metric helps to ensure that there is sufficient capacity to accommodate sudden increases in wastewater, such as those that may occur during events or when additional guests are present. This strategy is critical in commercial settings where water usage can be significantly higher and more variable than in residential situations.

In contrast, sizing based on the estimated annual volume or the average volume over a year would not provide the necessary capacity during peak times, potentially leading to system failure or environmental hazards. Similarly, the maximum volume over a month does not account for daily fluctuations and could misrepresent the daily demands on the septic system. Therefore, the focus on the daily (24-hour) peak volume is aligned with best practices for effective septic system design and function.