What is not the cause of grease buildup in a sewer?

• A. inorganic wastewater
• B. dip in pipe
• C. low velocity
• D. bad grade

Answer: (A)

Grease buildup happens when fats, oils, and grease (FOG) mingle with other organic solids and stick to the pipe walls, especially where flow is slow. A dip in the pipe creates a low point where these materials can settle and accumulate. Low velocity reduces the shear forces that keep solids in suspension, so deposition is more likely. A bad grade, meaning insufficient slope, also slows flow and promotes accumulation of grease and solids. Inorganic wastewater, by contrast, lacks fats and oils to form the greasy layer, so it does not inherently cause grease buildup.