Can I vent all of this with only one roof penetration?

I am designing for new construction in northern Utah, which has adopted the 2006 IPC.



2 floor drains: 2", no load

laundry group: 3 d.f.u.
laundry sink: 1.5"
washer: 2"???

kitchen group: 2 d.f.u.
kitchen sink (+possible future DW): 1.5"

bathroom group: 5 d.f.u.
tub/shower: 1.5"?? (says code, but would 2" be ok/better)
wc: 3"
lav: 1.5"

I would like to avoid poking two holes in the roof to vent this. Is that possible?

Is there any reason to prefer #1 or #2 as the location of the kitchen sink?

Is the mechanical room big enough, i.e. comfortable to work in? (small furnace/boiler/GSHP, water heater, water softener)


I could switch the locations of kitchen and mech/laundry, if necessary.

Yes, just run a 2" vent across the kitchen from the mech laundry plumbing wall and connect to the 3" vent at the water closet. Done all the time. Costs a bit more, but not that much.

As to the kitchen sink either location #1 or #2 is fine and the same cost. I would run the 2" kitchen rough in in the wall between laundry and mech to keep all the piping/ vent runs short

Thanks. That's what I thought, but I am a newbie and the codes are so hard to read/understand.

I almost wonder, however, if 10 feet of 2" pipe, an elbow, and a tee really cost more than the extra flashing material and vent cap. (or maybe it doesn't need a cap?)

As I thought about it, switching the kitchen made the plumbing runs much shorter. I also like the idea of puting the kitchen sink vent in the laundry/mech wall.

Well its not a lot more, but you really only need one more roof flashing for a 2" pipe, probably $15 ish. No vent cap required. It's also the extra time you need to run the pipe 10 feet and hang it with a few straps. But not that big a deal either.

You could put the laundry tub waste behind the lav and do a single back to back waste and vent for the two fixtures.

Check your dryer location as the vent run is going to be a problem from the inside wall to the exterior. Think its either 12' or 15' total run and an elbow is 3-5 feet. Check the manufacturers data. That would be lots easier on an exterior wall. You could go with a stacked washer / dryer and then put a small linen closet where the dryer was going....