Displacement, surge capacity and equilibrium water level
This video demonstrates displacement, surge capacity and equilibrium water level:
The red arrow in the diagram below shows where the equilibrium water level for the whole system is set.
In the whole system construction page, red arrows show where the equilibrium water levels are for each part of the system. The primary treatment digester, secondary treatment vermifilter and irrigation pages also show equilibrium water level for each component with red arrows.