I live in a high rise condo which was originally built without washer/dryers in units.

Almost everyone who remodels adds a unit in various places. They are European style stacked and ventless. Mine are Bosch.

The requirement is that they be low flow and installed by a licensed plumber approved by the building.

Mine are installed in a portion of a closet in the master bedroom which backs onto the master bath. In some way it ties into the main drain pipes in the building that run behind the closet. Other people have put them in the guest bath or master bath and I would imagine also tap into one of the common drain pipes that service a stack of units.

I have no idea what your building means by a drain because the units don't have a separate "drain" like a shower or bath has a drain but tie into one of the waste pipes. When I converted my shower tub to a walk in shower I had to change the drain to a larger drain as the larger drain is needed for a shower versus a bath. For this I had to get permission from my downstairs neighbor in order to access the drain from below - which meant that his ceiling had to be opened up and then patched.

If you do install a unit make sure that you have a water alarm system that shuts off as well as a Smitty pan to avoid damage to your unit as well as potentially catastrophic damage to units below you. My Bosch also has very heavy duty hoses that are double as an extra measure against possible leaks and floods.

Thank you Helen. this is helpful. the thing is, unless I can find a way to somehow toggle between the new washer and the shower, it doesnt sound as though we can move forward. We are apparently only allowed to have 2 tubs or 1 tub and a washer. i’d like to have 1 tub, 1 shower, and a washer.

Your plumber needs to be able to explain Drainage Fixture Units to the board. I can't imagine that a 3" line cannot take a washer drain with no problems, as it only adds 2-3 DFUs.