trying to correct WM drain, add vent and sink, and meet code

Hello all,

Thanks much to Terry and all the contributors. I use this site often and have always found all answers I need in the archives but, this time, I need more help.

I have a washing machine installed in a closet that currently drains into a 1.5" drain, unvented. The run from the WM to the DWV stack/soil pipe is roughly 20', with correct slope, but generally horizontal. There is an S trap below the standpipe.

To the left of the washer/dryer closet is a utility room (boiler, et cetera) but, separated by a pocket door and chimney (thus no direct access), kitchen to right, dining room behind with built-ins I'm loathe to tear out. The WM drain exits through back wall, downward to crawlspace, and then a horizontal run to DWV stack on far side of house. Bedroom floor above so, I can't go straight up with vent.

I'd like to add a sink to the utility room, tied into the WM drain. While doing so, I would like to increase WM standpipe to DWV stack run to 2". I was thinking I could move the WM trap to the crawlspace, add the vent, which would follow the additional drain to the utility room, where I can run an auxiliary vent up, through ceiling, crawlspace (house is a Cape) and through roof.

The house is in Connecticut (IRC I believe). The project will not be inspected but, I'd like it functional, not smelly, to code, and capable of handling new fast pumping washing machines.

I'm on an iPad dealy and the only drawing program I've got, you use your finger so, this is really crude. Sorry. Black is existing, all else as noted. Drawing meant to be in perspective, from crawlspace, looking at back of washer. The gap between the washer is filled with a pocket door and chimney so, the access between both is through the crawlspace. I thought I had it with this plan but, then I saw something about IRC code not allowing auxiliary vent to run horizontal before flood rim of lowest served appliance so,...ummm, help, please.

Thanks,
Michael

The washer p-trap needs to be on the same floor as the washer. The reason being is to prevent the standpipe from being too tall, therefore allowing the trap to siphon. There is a limit as to how long the standpipe can be.
The p-trap needs to be vented. If you can't run through the roof, then use a studor vent or AAV.
Some locals require a 3" waste line if you are dumping a washer into the line. The sink or lav will need venting too. The washer and the sink vent can be tied together, that way you can get by with one AAV, which will need to be exposed to open air to allow it to work. It can be in an enclosed space.

What you have drawn is NOT an "auxilliary vent", (whatever that is anyway, since if you have a vent, you do NOT need an auxilliary one), but rather a "secondary drain" when the regular drain gets plugged. The limit on the height of a standpipe is NOT to prevent siphoning, but rather to prevent trap seal loss due to inertia of the falling/moving water, although the end result is the same as if it had siphoned.

Thank you Terry and HJ.

I will go with AAVs in both locations and look into the 3" waste line requirement.

I truly appreciate the assistance.

Best Regards,
Michael