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.
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.
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.
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.
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