Washer/dryer in unit

I am no expert in the renovation world. That said, you need to connect the washing machine to a drain stack at least 3" wide. An engineer can create the drawings. I suspect, but do not know that you will need to file with the Dept of Buildings and also plan to hire an expediter.

You could also try going direct to a plumber; some larger or commercially-focused shops would be able to generate the sketch for management-review purposes, especially if you can provide the floor plan including riser pipe locations.

Filing would technically be required -- all alterations to plumbing count -- but you may be able to do this as an LAA application (which the plumber typically files) rather than an alteration (design professional and expediter, DOB plan review, etc.) since it sounds like it's not part of a larger job.

Thanks, Uptown_Joe, we can connect it to the drain stack from the adjacent sink. I suppose that would be at least 3: wide. Would you please tell me what an LAA application is? Using the plumber sounds like an excellent idea.

fatrabbit, be very careful- while it is possible your sink could connect to a drain stack at least 3" wide- you have to know for sure. A washing machine puts out a lot of pressure during the draining process- and if you don't have the appropriate width drain stack along with proper ventilation to handle the pressure- you could cause flooding in other apartments.

Thanks very much, semerun. I will make sure the drain stack is the appropriate width before we proceed..

LAA info (the plumber should know best, since they live and breathe this stuff, but this official page will get you the background):
http://www.nyc.gov/html/dob/html/development/laa_home.shtml