Don, never have I installed a kitchen sink with an 11/2 diameter pipe ALWAYS 2″
I also never use less then a 2″ waste pipe for any washing machine as the volume being pumped could very easily tax the system in volume.
Now consider the following
1- Kitchen sink lots of grease and soap scum build up if you have a garbage disposal it makes it even worse
2- Laundry lots of lint and soap scum combined with the grease and undersized piping to boot.
Now you being from the left coast with Boxer and Feinstein I guess anything goes but
I would normally install a separate line 2″ with a stand pipe and trap and vented line for all my washing machine installations.
The venting requirements differ from each state I use the following guide lines.
A trap shall be with in 2 feet of a vent line (except floor drains then I use no more then 15 ft) and the fixture should be with in 2 feet of the trap horizontal 4 ft vertical
I cannot see how the left coast figured in a suds pressure zone using such undersized piping.
What provisions are you allowing for shock adsorbing from the solenoid valves?
What preventive measures are you figuring for back flow preventing?
Are you planning on installing a house keeping pan for the over flow of water?
This sir is a time bomb just waiting to over flow on the folks below.