What is a primary factor contributing to the risk of septic system failure?

The primary factor contributing to the risk of septic system failure is the high clay percentage in the soil. Clay soils are characterized by their small particle size and compactness, which significantly restrict water movement and drainage. This can lead to waterlogging, where the soil becomes saturated and cannot absorb additional wastewater from the septic system. When the soil cannot effectively filter and treat the wastewater, it increases the risk of system failure, resulting in potential backups and contamination of nearby groundwater sources or surface water. In contrast, soils with better drainage characteristics, such as sandy or loamy soils, allow for more effective absorption and treatment of wastewater, which reduces the likelihood of septic system issues.