Which type of soil is considered least suitable for septic system installation?

Clay soil is considered the least suitable for septic system installation primarily because of its poor drainage properties. The high compaction and small particle size of clay result in minimal permeability, which means that water does not flow through it easily. This leads to a higher likelihood of surface water pooling and the inefficient treatment of wastewater, causing potential environmental hazards and system failure.

In a septic system, proper drainage is essential for enabling wastewater to be effectively filtered and treated as it percolates through the soil. Clay's ability to hold water rather than allowing it to drain can cause the system to back up or overflow, which poses significant health risks and can contaminate nearby water sources. Therefore, while other soil types, such as sand or loamy soil, may have their own characteristics impacting septic systems, clay soil specifically hinders the necessary movement and filtration of wastewater, making it the least suitable for septic installation.