A grease pit, as far as a restaurant owner is concerned, can be nothing but a money pit. Unless there is a recycling facility, the units provide no direct financial benefit to the restaurant, are expensive to install and require continual maintenance. Unfortunately, like a lot of things in life, grease collection and disposal is a necessary evil. The expense of not having grease interceptors is dramatic. I cannot calculate the billions of dollars saved in environmental damage and maintenance expenses of the public sewer systems thanks to grease interceptors. To balance the competing values of profitability for the restaurant owner and environmental protection, a grease collection system must be designed to meet performance criteria for the application and balance the economic restraints of installation and upkeep.
Both PDI and ASME codes provide guidelines for sizing. Sizing is based on the assumption that all fixtures being served discharge simultaneously. There is much debate over whether this assumption is truly reflective of the demand placed on the grease collection device. There is little opportunity for all fixtures and floor drains to discharge simultaneously. The reason sizing is so important is that typically the larger the unit, the greater the capital and installation cost. Installation of a grease collection system can contribute a significant portion of the capital cost for a restaurant start up. Depending on the type of operation, higher overhead costs may in turn put strain on the profitability of the enterprise and would be an economic barrier for a new entrepreneur. Economic barriers, in turn, hurt the economy. IAPMO classifies grease collection devices into Grease Traps and Grease Interceptors. IAPMO references any collection device larger than 750 gallons as an interceptor.