Onsite Wastewater management in Australia is based AS/NZS 1547:2012. State legislation calls in the standard and jurisdictions add guidelines to “clarify” specific design criteria. Deemed to Satisfy, also referred to as Acceptable Solutions are based on the more conservative criteria whereas performance criteria require a more detailed assessment of risk using the framework specified in AS/NZS 1547. Using the Deemed to Satisfy approach, the Design Loading Rate is based on soil type only and does not include other key site conditions such as slope, aspect, rainfall and average temperatures. This leads to huge variations in design.