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506.3.7 Prevention of Grease Accumulation in Grease Ducts
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Duct systems serving a Type I hood shall be constructed and installed so that grease cannot collect in any portion thereof, and the system shall slope not less than one-fourth unit vertical in 12 units horizontal (2-percent slope) toward the hood or toward a grease reservoir designed and installed in accordance with Section 506.3.7.1. Where horizontal ducts exceed 75 feet (22 860 mm) in length, the slope shall be not less than one unit vertical in 12 units horizontal (8.3-percent slope).
Grease duct reservoirs shall:
- Be constructed as required for the grease duct they serve.
- Be located on the bottom of the horizontal duct or the bottommost section of the duct riser.
- Extend across the full width of the duct and have a length of not less than 12 inches (305 mm).
- Have a depth of not less than 1 inch (25 mm).
- Have a bottom that slopes to a drain.
- Be provided with a cleanout opening constructed in accordance with Section 506.3.8 and installed to provide direct access to the reservoir. The cleanout opening shall be located on a side or on top of the duct so as to permit cleaning of the reservoir.
- Be installed in accordance with the manufacturer's instructions where manufactured devices are utilized.