What is the slope of a commercial grease duct that runs 80 feet long?

• A. 1 inch per foot
• B. 2 inches per foot
• C. 1/2 inch per foot
• D. No slope required

Answer: (A)

Grease ducts need a downward pitch so grease and condensation can drain toward a collection point, keeping the duct clear and reducing fire risk. Slope is measured as inches of drop per foot of run. For grease ducts, a common minimum is one inch of drop for every foot of duct. So an 80-foot run should have about 80 inches of total drop, ensuring the entire length is pitched to drain properly. A zero slope would allow grease to pool; a half-inch-per-foot slope is often not enough to ensure reliable drainage, while a two-inch-per-foot slope would be unnecessarily steep and impractical.