Residential sinks that have a garbage disposal require a minimum drain size of which measurement?

• A. 1 1/4"
• B. 1 1/2"
• C. 2"
• D. 1"

Answer: (B)

When a kitchen sink includes a garbage disposal, the drain must be large enough to handle the disposal’s discharge. The disposer grinds waste but still pushes out a relatively high volume of water and solids, so the pipe diameter must be substantial enough to prevent bottlenecks and frequent clogs. The standard minimum for residential kitchen drains with a disposal is 1-1/2 inches. Smaller sizes (like 1-1/4 inch or 1 inch) are prone to clogging under disposer use, while a 2-inch line would work but isn’t the minimum required. So, 1-1/2 inches is the smallest size that reliably accommodates a garbage disposal in most homes.