Conventional System

All wastewater from the household enters the septic tank.  The solids settle to the bottom of the tank and form a sludge layer.  The fats and greases collect at the surface, forming a scum layer.  Micro-organisms slowly break down the matter in both the scum and sludge layers.  Any material that cannot be broken down will gradually build up.  As a result the tank needs to be pumped out periodically by an accredited waste service provider (usually every 3-5 years).

The wastewater then flows, or is pumped, to a sub-soil bed or sub-soil trench for disposal.  The wastewater is distributed along the length of the bed or trench through a system of pipes.

Eventually, the wastewater is absorbed by the soil and/or plant roots around the disposal area.