Restaurant & Commercial Kitchen Drainage

A restaurant is four wet sites sharing one address

A restaurant can combine a wet kitchen and dish room, a delivery and refuse yard, a drive-thru or parking area, and a guest patio. Each zone has a different water source, cleaning method and loading. Map those zones before choosing a drain: a floor sink beneath equipment, a floor drain collecting washdown and a storm channel at a back door perform different jobs.

Start with the destination of each stream. Keep kitchen wastewater and contaminated outdoor wash water separate from roof and pavement stormwater. A drain collects liquid; it does not provide grease treatment, backflow protection or permission to discharge. Confirm the adopted plumbing and food codes and the sewer authority's requirements for the project.

Inside the kitchen: collect the right stream in the right place

Floor washing and the cleaning method

A point drain suits a floor graded toward one location; a grated channel can intercept a wider wash area or divide wet and dry work zones. Place either where staff can clean it without moving fixed cooking equipment. Avoid routing dirty floor water across food-preparation or clean-utensil areas. A long trench is unnecessary where a point drain and practical floor falls serve the room.

The FDA Food Code, §6-201.13, calls for drains, grading to drain and sealed, coved floor-wall junctions where water-flush cleaning is used. It is a model for local adoption, not a nationwide instruction to hose every kitchen. Coordinate drainage with the approved cleaning method; do not introduce water-flush cleaning into a room designed for another method.

Equipment discharge and indirect waste

Food-preparation sinks, ice equipment and warewashing equipment need a fixture-by-fixture waste schedule. A floor sink or hub receptor receives equipment discharge; its capacity, flood rim and access differ from a floor washdown drain. FDA Food Code §5-402.11 generally prohibits direct sewage connections from equipment holding food or utensils, with specified exceptions, including some connections permitted by local law. Resolve the required air gap or air break and any approved direct connection under the adopted plumbing code before setting equipment outlets.

Keep the specified separation above the receptor's flood rim and allow access to strainers. Do not place a receiving sink where overflow would run through a working aisle. Size for simultaneous discharge and batch dumps from the equipment schedule, including actual discharge temperature; daily water consumption is not a peak flow rate.

Grease management and approved discharge

Collect used fryer oil separately for approved recycling or disposal. Scrape food solids before washing. Route the fixtures identified by the approved grease-waste design through the required interceptor; toilet waste and clean rainwater do not belong in a kitchen grease interceptor. Dish-machine, disposer and mop-sink connections need explicit local review because permitted arrangements differ. EPA's food-service FOG guidance explains source control, separation and maintenance.

The listed Josam Lite Line JG-0100S grease-interceptor family is separate from Lite Line trench drains. Its manufacturer submittal describes an epoxy-coated fabricated-steel unit with removable baffle and flow-control fitting. Select the model by rated flow and grease storage, installation elevations, venting and service access—not connection diameter alone. A larger gravity interceptor or other approved arrangement may be necessary for the facility's discharge and maintenance interval.

Materials, floor connections and daily service

Sanitation and exposure: record cleaner and sanitizer names, working concentrations, contact time and maximum liquid temperature at the drain. Include descaling acids, chlorides and concentrated accidental spills. Evaluate body, grate, welds, seals, pipe and floor-joint materials together. ACO explains the additional chloride-corrosion resistance of 316L relative to 304; neither grade is permission to use any chemical at any temperature. Use the manufacturer resistance table as an initial screen and obtain compatibility confirmation for the actual cleaning schedule.

Waterproofing: select the drain connection for tile, resin or other specified flooring and its membrane. An anchoring/location flange is not automatically a membrane clamp or bonding flange. ACO's FloorDrain documentation distinguishes location-flange and mechanical-membrane options. Detail the membrane termination, floor joint, movement accommodation and support before pouring. Verify the specified water test before covering the assembly.

Traps, vents and cleanouts: coordinate the whole sanitary connection and any required trap-seal protection. Infrequently used floor drains can lose their water seal; a debris basket or odor cover does not establish an approved trap arrangement. ICC explains venting and evaporation protection. Keep cleanouts, trap access and interceptor covers reachable after equipment is installed.

Cleaning: remove collected solids instead of pushing them into the outlet. Provide tools and clearance to lift each grate and basket safely, clean the channel and outlet, and replace secured covers. Follow the drain and cleaning-agent instructions, with a documented schedule based on use. Inspect joints, seals, trap seals and grease accumulation; increase service when inspection shows buildup. Hot-water flushing does not replace interceptor cleaning. Protect food and utensils from splash during drain cleaning.

Exterior zones: keep rainwater and waste apart

The dumpster and grease-corral pad

Keep waste containers closed, prevent leaks, dry-clean spills and divert clean run-on away from the enclosure. EPA's restaurant stormwater guidance prioritizes these controls. A covered, contained area with collected wash water may be more appropriate than an open drain. Where a drain is provided, establish its approved wastewater destination and pretreatment before choosing the trench or basin. Do not send grease, mop water or mat-wash water to storm drains, dry wells or emitters.

The delivery apron and back-door threshold

Survey the sill, landing, apron and approach grades. Regrading or diverting roof water may solve the problem; a channel can intercept sheet flow upstream of the door when needed. Extend collection across the actual contributing flow path and check bypass around both ends. Door width plus a fixed two-foot allowance is not a hydraulic design. Preserve accessible landing geometry and account for pallet-jack wheels as well as delivery trucks.

Roof water landing where people work

An illustrative 4,000 sq ft roof receives about 2,490 gallons in a 1 in. rain, before losses or retention. Route leaders to the approved roof/storm system and keep emergency roof overflow functional and visible as required. Volume alone does not size a leader or channel: peak intensity, contributing roof area and downstream capacity matter. See downspout drainage.

Patio, sidewalk dining, and the front entry

Locate collection outside busy walking paths where practical. Where accessible surfaces cross a drain, ADA §302.3 limits openings to those that do not pass a 1/2 in. sphere, with elongated openings perpendicular to the dominant travel direction. Check the installed opening, adjacent gaps, slip resistance and level changes. Heel resistance is a separate selection consideration; a decorative pattern or brand label does not establish compliance.

The drive-thru lane

Use surveyed low points and sheet-flow paths to locate inlets. A channel across the approach or a basin at a low point can work, depending on grades and bypass. Rate the assembly for all vehicles allowed into the lane, including service traffic, and check braking and turning at the drain.

Landscape beds and the property line

Subsurface drainage collects soil water; surface channels collect runoff from paving. A conventional gravel-and-pipe French drain or NDS EZflow may address subsurface wetness after checking soil, outlet elevation and installation requirements. Confirm the required configuration and availability. Neither is an outlet for kitchen wastewater.

Everything downstream of collection

Storm connections, permitted daylight discharge, pop-up emitters and dry wells serve different site conditions. Infiltration needs soil, groundwater, setback and water-quality review. Keep contaminated service-area liquid in its approved waste system; a grease interceptor does not authorize stormwater discharge. Confirm receiving levels, detention requirements and any backwater or pumping provisions before fixing outlet elevations.

Reading the water: flow, capture and outlet limits

Use a channel to intercept a broad flow path and a point inlet where the grading concentrates water. Either can fail when water bypasses the opening or the downstream system surcharges. Design a safe overflow route away from doors and food-storage areas, and allow for partial blockage by litter or solids.

Illustrative exterior calculation: a 20 ft × 30 ft pad plus a 40 ft × 30 ft apron totals 1,800 sq ft, or 0.0413 acres. If the entire area is an approved stormwater catchment, assume C = 0.95 and a locally selected intensity i = 4 in./hr solely for this example. The customary U.S. rational-method approximation Q = C × i × A gives 0.157 cfs, about 70 gpm. Select design intensity for the local return period and time of concentration; do not combine a wastewater enclosure with storm runoff merely to reuse this example.

A 4 in. channel is not proven adequate by that result. Check grate capture at the approach slope, channel depth and fall, flow accumulation, outlet losses, receiving water level and downstream pipe. As a separate screening calculation, Manning's equation with actual internal diameters of 4 and 6 in., n = 0.011 and slope = 0.01 ft/ft gives about 101 and 298 gpm running full. These are uniform-flow pipe estimates without entrance losses or surcharge, not guaranteed outlet capacities. Use the FHWA drainage design guidance and selected assembly data.

Interior design starts with fixture and equipment flows instead of rainfall. For illustration, a 20-gallon batch draining uniformly over one minute adds 20 gpm; two simultaneous 3 gpm wash hoses give 26 gpm total. A rapid initial dump can exceed that average. Check receptor splash, strainer blockage, trap and pipe capacity, and the interceptor's rated flow using actual equipment discharge data.

Provide floor falls that reach the drains without violating accessible-route or equipment requirements. A nominal 1%–2% surface fall is a design starting point where appropriate, not a universal kitchen or landing requirement. Size and slope drain piping under the adopted code; there is no universal 1% minimum that guarantees greasy solids will move. Use the runoff calculator and runoff guide for exterior screening.

Load class: evaluate the complete installation

Record loaded wheel or axle forces, wheel contact area, hard versus pneumatic tires, speed and turning or braking. Small hard pallet-jack wheels can matter inside; refuse-truck wheels and slab-edge support matter outside. Select the channel or basin, frame, grate, fasteners and concrete support as a documented assembly.

• EN 1433 A15 — 15 kN test force; pedestrian and cyclist-only areas.
• EN 1433 B125 — 125 kN; pedestrian areas and car parks, subject to actual traffic.
• EN 1433 C250 — 250 kN; kerb and road-edge locations, not a blanket truck-aisle rating.
• EN 1433 D400 — 400 kN; road traffic lanes and parking areas.
• EN 1433 E600 — 600 kN; locations with high wheel loads.
• EN 1433 F900 — 900 kN; locations with exceptionally high wheel loads.

These numbers are test forces, not allowable vehicle weights. NDS letter classes and ASME floor-drain grate ratings use different conventions; NDS Class D does not mean EN D400. H-20, HS-25 and AASHTO M306 also need applicable documentation. See the load recommendation guide. A metal grate alone does not upgrade an unsupported plastic basin or establish an installed traffic rating.

Product options, zone by zone

Next door on the same site

Coordinate this guide with the dumpster pad, loading dock and patio and sidewalk guides. Larger production operations should also review food and beverage processing drainage for their process-water and hygiene requirements.