Traps must be sized for peak throughput, not average. An undersized trap fills during service and simply passes grease straight through, which is worse than useless because it creates false confidence.
Servicing frequency depends on volume: monthly is standard for a busy kitchen, quarterly for a light-use cafe. Keep the documentation.
Combine the trap with staff habits — scrape plates before rinsing, strainers in every sink, never pour hot fat away — and FOG problems largely disappear.