There is a 25% rule that applies to both grease interceptors and grease traps that states the FOG (floats to the top) and solids (settles to the bottom) content of the device should not be in excess of 25% of the grease interceptor/trap depth. Typically, cleaning frequencies for grease traps may be in the range of daily to weekly. Cleaning frequencies for grease interceptors can be expected to be monthly or quarterly.
This 25% rule allows the wastewater enough residence time inside the device to effectively remove the FOG and solids from the wastewater before it reaches the sanitary sewer system.
The single most important thing you can do to help extend the length of time between maintenance and saving your facility in maintenance expense is to use diligence in dry cleanup prior to wet cleanup. Scrape food debris in the garbage and dry-wipe the dishes prior to immersion in hot water (sink or dishwasher).