Conventional systems
Most conventional septic systems consist of a septic tank and drainfield.
The septic tank is a
watertight tank designed to separate solids and liquids in waste water.
The primary treatment occurs in the septic tank in an environment that
does not contain oxygen. Once the solids and liquids are separated, the
solids settle to the bottom of the first compartment. Over time these
solids accumulate and must be removed to ensure lawful performance. The
tank must have its solids pumped out every 3-5 years.
The drainfield is a
network of trenches spaced 9 feet apart on center that follow the
contour of the land. Water flows from the tank into the trenches where
it is absorbed into the soil. The soil environment acts as the final
treatment of that wastewater. Conventional gravel trenches are
generally 24-30 inches deep and 36 inches wide. The bottom of the
trench is filled with clean stone to a depth of 12 inches.
Gravel-less trenches are
the same depth as gravel trenches in most cases, but have some other
material other than gravel, usually plastic, in the trench. Some
gravel-less systems offer a reduction in the linear footage over gravel
systems.
The linear footage of
the drainfield is determined by the size of the facility and the soil
type. The more waste water generated, the larger the drainfield will
have to be in order to dispose of the wastewater.
Overview of other systems
These types of systems
are usually used when site constraints limit the installation of a
conventional septic system. Usually these constraints are available
space and soil depth.
Types of other systems are:
- PPBPS - Prefabricated permeable block panel system
- Subsurface Drip Irrigation
- Low Pressure Pipe