A septic tank (or black water) is a system that uses useful bacterial to break down and process the bio products of human waste into a stabilised liquid (known as effluent). The effluent is discharged from the tank into evaporation, a transpiration and or absorbtion trench system.
An absorbtion trench lets the effluent absorb into the soil. The grass and plants use the moisture and nutrients, and the wind and sun assist with evaporation.
Septic tanks need to be checked annually. How often they need to be cleaned depends on the tank’s capacity, the flow of wastewater and the volume of solids in the wastewater.
Some systems may need the solids (sludge) to be removed. This process is recommended every three to five years.