Daily Code Talk #59: IMC 506 Part 2 (506.3.7–506.3.9)

If grease can pool, it will. IMC 506 Part 2 is the “drain it and clean it” section for Type I hood grease ducts.🧠 Plain-English Highlights• 506.3.7 slope to prevent pooling– Route/install so grease cannot collect. Provide continuous slope toward the hood or a grease reservoir.– Minimum slope: 1/4 in per 12 in (2%).– If horizontal duct exceeds 75 ft: slope increases to 1 in per 12 in (8.3%).Exception: Factory-built grease duct follows its listing/manufacturer instructions.• 506.3.7.1 grease reservoirs (when used) must:– Bottom of horizontal duct or riser.– Full duct width, min 12 in long, min 1 in deep.– Bottom sloped to a drain.– Include a cleanout with direct access (typically on side/top).– Follow manufacturer instructions if it’s a manufactured device.• 506.3.8 cleanouts and openings:– No openings unless needed for operation/maintenance.– If sections can’t be cleaned from hood or discharge: cleanouts max 20 ft apart and within 10 ft of turns >45°.– Doors must be liquid-tight, steel (same thickness as duct), no fasteners penetrating duct wall, and gaskets/sealants rated 1500°F.• 506.3.8.1 personnel entry option: – If duct is large enough, provide at least one approved/listed 22 in x 20 in opening in horizontals and at top of risers.– With personnel entry, the standard cleanout spacing in 506.3.8 is not required (but supports must handle the extra load).• 506.3.8.2 in-line fan cleanouts: Provide cleanouts on inlet and outlet sides within 3 ft of fan duct connections.• 506.3.9 horizontal cleanout specifics:– Max 20 ft spacing and within 10 ft of turns >45°.– Bottom cleanouts only if no other location works and must include internal damming to prevent pooling.– Minimum opening 12 in x 12 in (or 12 in on one side where constrained).– Place cleanouts at reservoirs and within 3 ft of horizontal discharge fans.🏗️ Why it mattersMost grease duct failures are predictable: flat runs, missing cleanouts, or cleanouts placed where nobody can service them.🗺️ Where to show it• M-101: Slope arrows + slope rate on every horizontal grease duct run.• M-601: Tag cleanouts (CO-1, CO-2) and note spacing intent.• Details: Cleanout door detail and access coordination when ducts are wrapped or in enclosures.✅ Do• Draw the slope direction and rate.• Lay out cleanouts like a maintenance system, not an afterthought.⛔ Don’t• Don’t leave long “flat” grease ducts.• Don’t hide cleanouts behind hard ceilings/equipment with no access.🔧 Field tipUse a quick “20-10-3” check during layout: cleanouts every 20 ft, within 10 ft of any turn >45°, and within 3 ft on both sides of any in-line fan. Tag them CO-# so the access plan is obvious.Comment “IMC506-P2” if you want a paste-ready cleanout tagging legend and M-001 note.