Thanks, Terry.
All my DWV plumbing is to the inside of the exterior wall (partly below grade, w/ concrete to 31" above floor).
To conceal most of the pipes, I've kept supply and waste plumbing to within 10" of the wall and have begun to build a "housing" topped by a shelf at 39" above the floor [see photos].
I want to install the outlet box in the face of the housing to reduce the clutter in front of the wall. There will still be 3 vertical pipes extending above the shelf, unfortunately.
The position and height of the stand pipe is constrained by the position of existing vent pipes, a tub drain from upstairs (separately vented), and the position of the 3" drain exiting thru the floor [see photos].
Based on good advice from your forum in the past, I think I did the DWV plumbing correctly, but I did not have a digital camera at the time. Would you be willing to look at my Rube Goldberg solution and let me know if it's functional if not to code?
The bottom of the standpipe trap is 15.5" above the floor and the top of the standpipe is presently 24" from the junction with its trap. I plan to strap it to the frame of the housing and cut it so the washer drain line can also go into the face of the housing, rather than thru the shelf.
Please ignore the non-square, non-plumb work--at least it doesn't leak!
A