On what basis are OSSF systems normally sized?

On-site sewage facilities (OSSF) systems are typically sized based on hydraulic loading, which refers to the amount of wastewater generated per unit of time that the system must handle effectively. Hydraulic loading takes into account factors such as the number of bedrooms in a home, expected water usage, and the type of practices for wastewater treatment and disposal. Sizing the system correctly based on hydraulic loading ensures that it can adequately treat and disperse the wastewater without causing a hazard to public health or the environment.

When hydraulic loading is properly assessed, it provides a reliable metric for determining the capacity of various components of the OSSF, including the septic tank and the drain field. This consideration helps to prevent issues such as system overload, which can lead to system failures, odors, and contamination of groundwater.

While lot size, soil profile, and homeowner's preference may influence the overall design and installation of an OSSF, they do not primarily dictate the sizing of the system in terms of its capacity to handle wastewater. Therefore, hydraulic loading stands out as the key factor in sizing OSSF systems effectively.