Previous UPC code allowed a laundry tray to wet vent over a washer if it was 2" pipe.
Strict interpation of the code allows wet venting for bathroom groups, and not for the washer and sink combo.
I'm trying to add a sink in our laundry room. My questions are mostly about the drain and vent. I understand the ideal would be as this photo that I got from other post on this site.
In this photo, the black lines I have added are to show what is already in place but you cannot see. The two vertical lines at left and right are studs. The vertical box next to right stud is gas pipe. Diameters are standpipe (2"), drain-vent below clean out (2.5"), vent above clean out (2").
I can easily T into drain-vent pipe for sink drain, and I can easily connect and run hot and cold water lines for sink. My problems are with sink drain and vent for washer standpipe. The only place I could possibly put additional vent would be right after trap for standpipe to left of studs. Then I would need to run it vertical and cut through studs to connect with vent.
My main question for you experts: is that really necessary? Please help me understand risks if I just T sink drain into drain-vent pipe above where line connects from washer and below clean out. Where the standpipe trap now connects to the drain-vent is at a downward Y, so I'm not seeing much risk of the water from sink drain siphoning from standpipe trap.
Thanks in advance for your help!
P.S. I'm sorry I could not figure out how to delete this additional image where I first incorrectly showed T instead of Y now connecting to drain-vent.
Terry, many thanks for your reply. Can you clarify when the code changed to no longer allow wet vent over a washer? I'm asking because we are under 2006 IPC. Section 908.3 (Common Vent - Connection at different levels) seems to describe what I'm proposing, so maybe I'm okay.
It says, "Where the fixture drains connect at different levels, the vent shall connect as a vertical extension of the vertical drain. The vertical drain pipe connecting the two fixture drains shall be considered the vent for the lower fixture drain, and shall be sized in accordance with Table 908.3. The upper fixture shall not be a water closet."
Section 909 (Wet Venting) refers only to bathroom groups as you noted, but how is the vent for lower fixture in Section 908.3 not a wet vent? If it is, then it seems the difference with Section 909 (at least in 2006 IPC) is that for bathroom groups only you can have more than two fixtures connected.
Even if I'm reading correctly that 2006 IPC says I'm allowed to connect as I described above, I'm interested in any other thoughts as to why it might be a bad idea. I don't want to break the law. That's for sure. But as with many other things you can do legally, being legal does not mean good idea.