Grease Trap Parts & Diagram
Identify every component inside your grease trap with our interactive cross-section diagram. Click any part to learn its function, common failure points, and replacement cost.
What You'll Learn
Whether you're troubleshooting a failing grease trap, ordering replacement parts, or explaining an issue to your plumber, understanding what's inside the tank matters. This guide covers every component in a standard grease interceptor — from the access lid down to the solids that settle at the bottom.
Use the interactive diagram below to explore each part visually. Click any highlighted component to see what it does, what goes wrong, and what replacement typically costs. Below the diagram you'll find a complete parts reference table and a comparison of under-sink versus in-ground trap components.
Interactive Grease Trap Diagram
Click any highlighted part to view details. The cross-section below shows a standard two-compartment grease trap during normal operation.
Replacement Cost:
Grease Trap Parts Reference Table
Use this table as a quick reference when ordering replacement parts or discussing service needs with your contractor.
| Part | Function | Common Issues | Replacement Cost |
|---|---|---|---|
| Access Lid | Provides entry for inspection, cleaning, and pump-outs; seals the trap to contain odors | Cracking, warping from UV exposure, corroded hardware, missing gasket seal | $50 – $300 |
| Inlet Baffle | Slows incoming wastewater flow and directs it downward to promote FOG separation | Corrosion, shifting out of position, buildup restricting flow | $75 – $250 |
| Outlet Baffle | Prevents floating grease from exiting the trap into the sewer line | Cracking, grease bypass due to damage, incorrect height after replacement | $75 – $250 |
| Flow Restrictor | Controls the rate of wastewater entering the trap to ensure adequate retention time | Clogging with food debris, incorrect sizing after replacement | $20 – $80 |
| T-Fittings | Direct flow downward at inlet and outlet to draw from the clear water zone rather than the grease layer | Corrosion, clogging, breaking during pump-out service | $30 – $120 each |
| Gaskets & Seals | Create airtight and watertight seals at lid, pipe connections, and access points | Dry rot, compression loss, odor leaks, improper seating after service | $10 – $60 |
| Vent Pipe | Allows gases to escape and prevents pressure buildup that could force grease through the outlet | Blockage from grease buildup or debris, disconnection, code-noncompliant routing | $40 – $150 |
Under-Sink vs. In-Ground: Grease Trap Parts Comparison
Not all grease traps are built the same. The parts you'll encounter depend on whether your facility uses a small under-sink unit or a large in-ground interceptor. Here's how the components differ:
Under-Sink Grease Traps
- Capacity: 8 to 100 GPM, typically 20–50 lb grease capacity
- Lid: Stainless steel or plastic; removed manually for cleaning
- Baffles: Usually one or two removable plastic or steel baffles
- T-Fittings: Small diameter (1.5″–3″); often integrated into the unit
- Flow Restrictor: Built into the inlet on most models
- Gaskets: Rubber lid gasket; replace every 1–2 years
- Vent: Often vented through existing kitchen plumbing
In-Ground Grease Interceptors
- Capacity: 500 to 5,000+ gallons; handles entire kitchen output
- Lid: Heavy concrete or cast iron; requires tools or machinery to open
- Baffles: Large concrete, fiberglass, or steel walls dividing tank into compartments
- T-Fittings: Larger diameter (4″–6″); accessible through manholes
- Flow Restrictor: Separate inline device upstream of the interceptor
- Gaskets: Heavy-duty rubber or bituminous seals; longer lifespan
- Vent: Dedicated vent pipe through grade level; code-mandated sizing
Frequently Asked Questions
A standard grease trap consists of an access lid, inlet pipe with baffle or T-fitting, primary and secondary baffles that slow water flow, an outlet pipe with baffle or T-fitting, a flow restrictor, gaskets and seals, and a vent pipe. During operation, the tank contents separate into three layers: a floating grease layer on top, a clear water zone in the middle, and settled solids at the bottom.
Grease trap baffles typically last 5 to 15 years depending on material and exposure to chemical cleaners. Inspect baffles during every pump-out. Replace immediately if you see warping, cracking, heavy corrosion, or if the baffle has shifted out of position. A damaged baffle allows grease to bypass the trap and enter the sewer line, which can trigger FOG violations.
Minor parts like gaskets, seals, and access lid hardware can typically be replaced by facility maintenance staff. However, baffles, T-fittings, and flow restrictors should be handled by a licensed plumber or grease trap service professional. Incorrect installation can void warranties, create code compliance issues, and cause the trap to fail prematurely.
A baffle is a vertical wall or plate inside the trap that forces wastewater to flow under or around it, slowing the flow and giving FOG time to separate and rise. A T-fitting is a T-shaped pipe fitting at the inlet or outlet that directs water flow downward below the grease layer, preventing floating grease from exiting through the outlet. Many modern traps use T-fittings in place of or alongside traditional baffles for improved separation.
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