Commercial KitchenDrainage Solutions

Grease interceptor sizing is based on fixture drainage flow rate and local code requirements. Most jurisdictions follow the PDI (Plumbing and Drainage Institute) sizing formula or UPC/IPC code calculations. Factors include number of fixtures draining to the interceptor, flow rates, and retention time. A typical restaurant might need a 50-100 GPM interceptor. Consult local authorities and PDI G101 for proper sizing.

Grease traps (also called hydromechanical grease interceptors) are smaller, typically 10-100 GPM, installed inside or near the kitchen. They require frequent cleaning (often weekly). Grease interceptors (gravity grease interceptors) are larger, buried outside, and are pumped less frequently (monthly to quarterly). Many codes distinguish between them by capacity or retention time.

Kitchen cooking areas typically require NSF-certified stainless steel floor drains with deep seal traps (4" minimum), sediment baskets, and grease-handling capacity. Drains must connect to a grease interceptor in most jurisdictions. Heel-proof, ADA-compliant grates are standard. Size floor drains for expected washdown volume - typically 6" to 12" diameter.

This varies by jurisdiction. Many codes exempt dishwashers from grease interceptor requirements because the hot water and detergent can emulsify grease and potentially disrupt interceptor operation. Check local regulations. Where required, dishwashers may drain to a separate interceptor or require temperature management. Always verify with local plumbing authority.

3-compartment sinks require indirect drainage via an air gap to a floor sink or floor drain. The floor sink must connect to the grease interceptor. Size the floor sink for the sink discharge volume. Include basket strainers to capture food solids. Position floor sinks close to the 3-compartment sink to minimize floor piping.

Cleaning frequency depends on interceptor size, kitchen volume, and local regulations. Most jurisdictions require pumping when grease and solids reach 25% of capacity. Typical schedules range from weekly (small traps) to quarterly (large outdoor interceptors). Maintain cleaning records for health department inspections. Some areas require specific pumping intervals regardless of capacity.

AGRDs are mechanical devices that automatically skim and collect grease from the interceptor, typically storing it in a separate container. They maintain interceptor efficiency by preventing grease accumulation. AGRDs can reduce pumping costs but require regular collection of skimmed grease. They must be PDI-certified where required.

Commercial kitchen trench drains should be stainless steel (304 minimum), NSF-certified, and sized for washdown volumes. Pre-sloped channels ensure positive drainage. Grates must be heel-proof (max 1/4" openings) and handle expected traffic. Connect to grease interceptors. Common widths are 4" to 8". Include cleanouts every 20-25 feet.

Walk-in coolers need floor drains for defrost water and cleaning. Use freeze-resistant designs with heating elements in freezer areas. Deep seal traps prevent odor issues. Drains may need to bypass grease interceptors since cooler drainage doesn't typically contain grease. Check local codes for cooler-specific requirements.

Commercial kitchen floors should slope 1/8" to 1/4" per foot toward floor drains. Steeper slopes (up to 1/4" per foot) in high-volume areas like dish rooms and pot wash. Floors must be slip-resistant even when wet. Quarry tile, sealed concrete, or epoxy coatings are common. Proper slope prevents standing water that creates slip hazards and bacterial growth.