Australian properties run two independent drainage systems: sanitary (sewer) and stormwater. Stormwater collects from downpipes, surface pits and paved areas, discharging to the street kerb, an underground council network or approved on-site soakage.
Illegal cross-connections — stormwater into sewer or vice versa — cause sewer overflows in rain and contaminate waterways, and are a standard check during drainage inspections.