Drainfield Soil

It is an often-overlooked fact that soil plays a major part in the proper functioning of a septic system. Overlooked, that is, until it fails. Soil failure accounts for most of the incidents of septic system failure.

The role of soil is that of a fine filter, and the home to trillions of microscopic organisms that feed on organic matter in the effluent from the drainfield.

Soil Types

Soil texture determines how quickly wastewater will be absorbed in the drainfield. The ability of soil to absorb water is known as soil percolation. Soils containing a balance of coarse and fine particles are the best types for drainage, or percolation, of wastewater.

Gravel, or soil with a coarse texture, or coarse sand may allow wastewater to pass too quickly to provide adequate treatment. These types of soils work only if they are deep. In some areas of the country mound systems using imported soil are used where these soil conditions exist.

Clay Soil

Many soil mixtures contain fine particles of clay. This type of soil can be used in drainfields, but water moves through it much slower than in gravel or coarse textured soil. Clay particles can swell and block soil passages slowing the movement of wastewater even further. Additionally, clay particles can electronically bond to sodium molecules contained in wastewater. This can lead to a soil condition known as hardpan. If soil becomes hardpan the passage of wastewater is totally blocked and drainfield failure will follow. There are chemical products available that can relieve hardpan conditions in clay soil. One such product is known as Septic Seep.