: I am remodeling a summer home and the kitchen drain is 1-1/2" copper all the way to the main stack with a separate 1-1/2" vent. I know that code requires a 2" drain beyond the trap but it will be difficult to change this. The drain is under a window and from the trap it makes a 90 degree left hand turn in the wall (horizontal with proper slope) past the window. The vent then tees off thru the roof and the drain continues another foot before making another 90 degree turn and connects to the 3" main stack 2 feet away. Can I leave this line 1-1/2". If not will a 2" long sweep 90 fit in a 2x4 90 degree turn. I cannot reroute the drain down and through the crawl space based on framing and and stack layout.
Although I only run 2" drain lines for a residential kitchen sink, some codes permit 1-1/2", check yours.