I cannot answer your question regarding depth behind the sink as my peninsula is 4 ft. wide to allow for a counter height bar behind the sink. However, I do have a 24" wide dishwasher and then a 3" support at the end for the granite and have found that 27" allows enough space for a comfortable working area with no water going onto the floor at the end. Just an added thought, why continue to drain dishes on the counter where you're dealing with draining water? With a Franke Orca sink, I wash on the left side with the greater front to back depth and drain on the right side of the sink. No more messy puddles on the counter, or floor, for me.

This post was edited by Texasgal47 on Wed, Apr 17, 13 at 21:38

You need a minimum 18" on one side of your sink and 24" on the other. The minimum front to back depth should be 36", but 42" is better if you're doing seating as the minimum recommended overhang for seating is 15" at counter height and you need to beef up the back of the cabinets to support the overhang or build a pony wall to hide the plumbing and attach the overhang support to. The 24" side of a sink can be the ideal location for your DW, but not if it's between the sink and range. That's your prep area, and you don't want to cross zones with your cleanup zone. That way, two people can use the sink at the same time if you don't have room to add a prep sink.