ASSESSING EXISTING GREASE TRAP CAPACITY: To estimate the minimum grease trap capacity required, you need to know your typical water consumption over the supply billing period (in cubic metres; shown in the second column from the right on your water bill) and both the total number of days and hours per day that the establishment was open over the billing period.
Table 1 on Page 4 gives the grease trap capacity (the volume of material that can be held, Column C) required for a selection of hourly water consumption rates (Column A). To calculate your hourly water consumption rate in litres:
A = 
Consumption from
water bill, cubic metres 
÷ 
number of working days over the billing period 
÷ 
working hours
per day 
x 1000 
Example:
A restaurant open 6 days per week, 14 hours per day has a typical water bill showing consumption of 985 cubic metres over a 120 day billing period. The restaurant was open 104 days during this billing period.
Therefore, A = 985 ÷104 ÷14 x 1000 = 677 litres/hour. From Table 1, the grease trap capacity required is around 970 litres.
The capacity of an existing grease trap in litres can be calculated from measurements of length, width and depth (in millimeters) and allowing for 2/3 of total trap depth to be occupied by contents.
Capacity = Length x Width x Total Depth x 2÷3,000,000
