How do I layout a welded grease duct slope so grease drains toward the hood?

Horizontal grease duct runs under 75 feet long must slope a minimum of 4 1 inch per linear foot (2% slope) back toward the commercial hood or an approved grease reservoir collection trap. If the horizontal run exceeds 75 feet, the slope must increase to at least 1 inch per linear foot.

['Horizontal grease duct runs under 75 feet long must slope a minimum of 4 1 inch per linear foot (2% slope) back toward the commercial hood or an approved grease reservoir collection trap. If the horizontal run exceeds 75 feet, the slope must increase to at least 1 inch per linear foot.']

Print Reading, Tags & Layout 3rd Year RED

Stop if

Use this as training guidance. The foreman, approved drawings, project specs, manufacturer installation instructions, employer safety policy, and AHJ/code requirements always control the final answer.

Steps

Stop and verify the approved detail, manufacturer instructions, foreman direction, and project specs before touching it.
Horizontal grease duct runs under 75 feet long must slope a minimum of 4 1 inch per linear foot (2% slope) back toward the commercial hood or an approved grease reservoir collection...

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how do i layout a welded grease duct slope so grease drains toward the hood?