What formulas, other than the Town of Cary formula, are available for sizing grease interceptors?
Sizing of grease interceptors is based on wastewater flow and can be calculated from the number and kind of sinks and fixtures discharging to the interceptor. In addition, a grease interceptor should be rated on its grease retention capacity, which is the amount of grease that the device can hold before its average efficiency drops below acceptable levels. The Environmental Protection Agency created a formula that relies on varying factors; e.g., type of highway, varying storage capacity factors, number of seats in the dining area, and gallons of wastewater generated per meal. The EPA recommended minimum size interceptor is 750 gallons. The Unified Plumbing Code also details a formula that relies on the number of meals served per maximum serving hour, waste flow rates from facilities with and without dishwashers and garbage grinders, and various retention times and grease storage factors. Both of these methods are somewhat subjective to individual interpretation. The Plumbing and Drain
