Does a Grease Interceptor Need PE Certification?

The sizing calculation is the engineering core. I build the fixture schedule for everything discharging grease waste: compartment sinks, prep and scullery sinks, dishwashers, cooking equipment with drains, and floor drains and floor sinks in food preparation areas. Each fixture contributes its code flow value, and the total flow determines the interceptor capacity needed for adequate retention — the dwell time that lets grease cool, separate, and float while clearer water exits. Where the utility publishes its own sizing method, I run that method and design to whichever governs. The connected-load honesty matters because kitchens change. I size for the permitted kitchen's equipment schedule, and I note where future equipment additions would exceed the interceptor — because the most common grease system failure is a kitchen that grew past its interceptor. The sealed drawings carry the sizing calculation visibly: fixture schedule, flow totals, the selected interceptor's rated capacity, and the code and utility references the sizing follows. That transparency is what lets the plumbing reviewer, the health reviewer, and the utility each confirm compliance from the same set.

The interceptor's physical design determines whether it works for its service life. I locate gravity interceptors for pump-truck access with manhole access to every compartment, set the inlet and outlet inverts for gravity flow at proper slopes, and design the venting — interceptors need venting per the code, and poor venting causes the flow problems that push grease past the device. Flow control fittings on hydromechanical units get specified and shown. The piping materials suit grease waste service, and cleanouts are placed where the maintenance crew can actually reach them. Utility coordination is a parallel permit track. I confirm the sewer utility's FOG program requirements — sizing method, approved devices, installation standards, and the maintenance agreement — and design to them from the start. The health department's review of the kitchen plumbing runs on the same drawings, so the grease waste design anticipates the food code's fixture and indirect-waste expectations too. The PE's sealed plumbing set is the single document all three reviewers — plumbing, health, utility — read, and it's designed to satisfy all three.

A grease interceptor submittal is ready for PE certification when the sizing, the physical design, and the utility coordination are all complete. The utility's FOG program is the requirement most often discovered late. • Fixture schedule complete: every grease-waste fixture tallied with code flow values • Interceptor sized from the flow calculation per the plumbing code and the utility's FOG sizing method — strictest governs • Interceptor type selected for the load and the utility's rules: gravity vs hydromechanical • Location designed for maintenance: pump-truck access, manhole access, proper inlet/outlet slopes and venting • Sewer utility FOG program requirements confirmed and met: approved devices, installation standards, maintenance agreement • Sizing basis documented on the sealed drawings: fixture schedule, calculation, and code references visible to every reviewer