Code Reference
PlumbingIPC 2021

Section 1003.1/Interceptors and Separators (Grease Traps)

IPC 1003 covers grease interceptors, oil separators, and sand interceptors required for specific waste types.

What this section requires

Grease interceptors are required for food service establishments where fats, oils, and grease (FOG) are discharged into the drainage system. The interceptor must be sized based on the number and type of fixtures connected, the flow rate, and the grease retention capacity. Interceptors must be accessible for cleaning and maintenance. Oil and sand separators are required for auto repair facilities, parking garages with floor drains, and other locations where petroleum products or sediment may enter the drainage system. Interceptors must not be installed in areas where they would be inaccessible for maintenance.

Why this section exists

Fats, oils, and grease solidify in drainage pipes as they cool, creating blockages that cause sewer backups and overflows. FOG is the leading cause of sanitary sewer overflows in the United States. Grease interceptors capture FOG before it enters the building drain and public sewer. Oil separators prevent petroleum products from contaminating the sewer system and the wastewater treatment plant. These devices protect both the building drainage and the public infrastructure.

What plan reviewers look for

Plan reviewers check the plumbing drawings for grease interceptors at every food service establishment. They verify the interceptor sizing based on the connected fixtures and flow rate. They check the location for accessibility (must be cleanable without entering hazardous or inaccessible areas). They verify that dishwashers and food waste disposers are connected through the interceptor, not bypassing it.

Common violations

No grease interceptor at food service
A restaurant, cafeteria, or commercial kitchen does not show a grease interceptor on the plumbing drawings. All food service fixtures that discharge FOG must be connected to an interceptor.
Interceptor undersized for connected fixtures
The grease interceptor is sized for only the pot sink but the kitchen also has a dishwasher, prep sinks, and floor drains that connect through the interceptor. All connected fixtures must be included in the sizing calculation.
Compliance tip
Show the grease interceptor on the plumbing plan with all connected fixture connections. Include the sizing calculation based on the connected fixture count and flow rates. Locate the interceptor where it is accessible for regular cleaning (typically every 30-90 days). Verify compliance with local sewer district requirements, which may be more stringent than the IPC.

Related IPC requirements

Section 1003.3 covers grease interceptor sizing methods. Section 1003.4 covers oil separator requirements. Section 702 covers the drainage system that receives the interceptor discharge. Local sewer authorities typically have additional grease trap requirements and maintenance schedules.

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Related sections

Table 403.1Minimum Plumbing FixturesIPC 2021702.1Drainage System Pipe SizingIPC 20211002.1Trap RequirementsIPC 2021