The size of a septic system is most commonly determined by what factor?

The size of a septic system is most commonly determined by the number of bedrooms in a property. This is because the number of bedrooms gives a good estimate of the potential occupancy of the home, which directly correlates to the amount of wastewater that will be generated.

When designing a septic system, health regulations often require that the system can accommodate a certain number of gallons per day for each bedroom, as it is assumed that the number of people living in the home, and consequently the volume of waste produced, will increase with more bedrooms.

While properties' size, the number of bathrooms, and soil type can influence certain aspects of septic system design—like the layout or the absorption capacity—these factors do not directly determine the necessary size of the septic tank and leach field in the same way that the number of bedrooms does. Thus, the primary consideration for sizing a septic system remains the number of bedrooms to ensure it meets health and efficiency standards.