When may a grease trap be installed?

A grease trap may be installed when an interceptor cannot be installed outside, as stated in the correct answer. This typically occurs in situations where there are physical limitations that prevent the installation of a full-sized grease interceptor outside the facility, such as space constraints, site layout, or other practical considerations.

Grease traps are smaller devices designed to retain grease and fats from wastewater, thereby preventing them from entering the drainage system. They are often used in situations where installing a larger interceptor outside would be impractical due to the aforementioned constraints. Therefore, establishing a grease trap inside can be a viable alternative to manage grease disposal effectively.

The other circumstances mentioned in the choices do not fully encompass the regulations governing the installation of grease traps. Grease traps are generally recommended in commercial kitchens and facilities with certain levels of grease output, rather than only in minor problems. Additionally, the flow limit of less than 20 gpm does not singularly justify the choice of installing a grease trap without considering the overall context of grease management in the facility. Lastly, while being a new facility could play a role in planning the installation, it is not a defining criterion since existing facilities may also require grease traps based on their use and discharge characteristics.