Weigh indoor versus outdoor siting for a new grease interceptor installation

Steps

1. Confirm which interceptor types are even permitted for indoor installation under the locally adopted plumbing code, since compact hydromechanical units are commonly approved for point-of-use indoor placement (under a sink or in a nearby floor recess) while large-volume gravity interceptors are typically designed for underground outdoor installation
2. Weigh space and construction cost tradeoffs: outdoor gravity interceptors require excavation, buried tank installation, and adequate site area, which can be infeasible in dense urban sites or older/historic buildings with limited or no outdoor footprint
3. Weigh capacity and service-frequency tradeoffs: larger outdoor gravity units generally hold more volume and can go longer between pump-outs, while smaller indoor hydromechanical units typically require more frequent cleaning due to limited storage capacity
4. Weigh odor and access tradeoffs: outdoor units are typically sited away from dining/customer areas specifically to manage odor, while indoor units require an access path for haulers and maintenance staff through occupied kitchen space
5. Where an outdoor gravity interceptor cannot be sited due to space constraints, evaluate whether the local FOG program allows a variance to use one or more smaller hydromechanical units with more frequent servicing instead, since several programs offer this pathway for physically constrained sites
6. Confirm any freeze-protection, traffic-loading (H-20 rating for driveway/parking installations), or setback requirements that apply specifically to outdoor buried interceptors in the local jurisdiction