Which type of soil is generally less effective in filtration for septic systems?

Clay soil is generally less effective in filtration for septic systems due to its physical properties. Clay particles are very small, which results in a tight compact structure that restricts the movement of water. This high density leads to poor drainage and can inhibit the percolation of wastewater, making it difficult for the system to properly treat effluent. When the moisture level is high, clay can become very saturated, which exacerbates its inability to filter contaminants from wastewater effectively.

In contrast, sandy soil is more porous, allowing water to flow through it quickly and facilitating better filtration. Loamy soil, a mixture of sand, silt, and clay, offers a balanced structure that supports good drainage and filtration. Silty soil, while finer than sandy soil, still allows a decent amount of water to percolate through, although it can retain moisture better than sand.

Given these characteristics, clay soil is not suitable for the infiltration process required in septic systems, which is why it is recognized as less effective in filtration compared to other soil types.