Thank you for your reply. I was busy doing my wiring rough and I passed!
So back to plumbing...
1) The usual configuration when the window is too low for the kitchen sink vent to rise up to at least 6" above the flood rim level before turning horizontal is to put the san-tee for the kitchen sink just outside the king stud for the window. Then the drain goes straight down and the vent goes straight up. The kitchen sink trap arm (which is 1-1/2") gets drilled through the studs (behind the dishwasher in your case, if you put it on that side) until it reaches a point where it can emerges into the kitchen sink cabinet, via either a LT90 or a 45. Note that the trap arm, which extends from the trap outlet to the san-tee and includes the pipe in the kitchen sink cabinet, is limited to 42" in length. Use stud shoes to reinforce the drilled studs, e.g. Simpson's HSS2 line,
https://www.strongtie.com/miscellaneousconnectors_woodconnectors/hss_studshoe/p/hss
Thank you for this I finally understand what you are saying. Found a couple illustrations to help me as well.
And the stud shoes I really appreciate. Helped remedy some worry
3) I don't follow your description of "3 acres across". The code section in question is UPC 904.1
https://up.codes/viewer/washington/upc-2021/chapter/9/vents#904.1 So you either need a minimum of a 3" vent through the roof (or the equivalent area, (2) 2" plus a 1-1/2"), or you need to use the exception. For that, you need to determine the minimum common building sewer size for both buildings (count DFUs and WCs); if it's 3" and the main house complies with 904.1 by having a 3" vent (or equivalent area), they your ADU satisfies the exception. Likewise if it's 4" and the main house has a 4" vent (or equivalent area).
I went a little too literal here. This is an ADU on the same 10 acre parcel as the main home and on a separate well & septic.
It will require the 3". That said- I am really fixated on tying into the one 3" vent stack. Not sure why, feels easier in my mind
My dilemma is whether to use the laundry wall because it is 2 x 6 or the bath wall which is only 2 x 4.
Can a 3" stack fit in a 2 x 4 wall and meet UPC? or do you go 2" to top of sill plate (attic area) from Lav or toilet and expand to 3" to tie in the rest of the dry vents and then VTR
But if the minimum common building sewer size is 4", and the main house has a 3" vent (or equivalent area), then a single 2" vent through the roof at the ADU will not satisfy the exception. You'd need a 3" vent through the roof, or (2) 2" vents, or a 2" plus (2) 1-1/2" vents. I.e. in this case the exception doesn't buy you very much over just complying with 904.1 directly.
4) The WC needs a vent path from its vent connection (wet vent via the lav drain) to the roof that is 2" minimum throughout.
I think I fixed this in new drawing
8) The way you've drawn the tub trap vent takeoff isn't actually possible--you can't replace the elbow portion of the p-trap with a san-tee for the vent-takeoff. The vent takeoff would need to be a horizontal combo (could be 2x2x1-1/2) with at least a short section (could just be an inch or two) of pipe between the p-trap outlet and the horizontal combo.
Yes I totally botched this one and my drawings aren't exactly easy to read.
I was trying to figure out how to utilize the exterior wall directly behind the tub to run a 1 1/2 vent either VTR or across to the main vent stack when the main drain line is in the opposite direction.
But if you do that, and if the tub vent rises vertically (which includes up to 45 degrees off plumb) to at least 6" above the tub flood rim before going horizontal (less than 45 degrees off plumb), then the tub is properly dry vented. And if the shower trap arm, from the shower trap outlet to the wye where the tub fixture drain joins it, is under 60" in length and 2" in total fall, then the shower is properly wet vented by the tub.
9) (New) The laundry sink and the washing machine standpipe each need their own dry vent takeoffs. The two dry vents can be 1-1/2" and combine to a single 1-1/2" vent at an elevation at least 6" above both fixture flood rims.
I see what you are saying- I didn't draw it correctly and did search for a UPC diagram/example for this one as well. Thanks so much for pointing that out.
[It is actually possible to vent both fixtures via a single vent takeoff if you use circuit venting; that would require that both trap outlets be at basically the same elevation, and that you have a horizontal drain connecting them at that elevation, with the vent takeoff in between the two fixture connections. That's probably more trouble that it is worth barring some unusual circumstance.]
Hopefully I am getting closer
Best,
Patty