I am plumbing in a cabin with limited attic space and my plumbing is on exterior walls. I feel that a vent on the toilet and washing machine are a must. I am wandering if I empty my 2" sink and shower drains into a 3" line that dumps into a 4" trunk line could I eliminate the vents on those fixtures. I have no code to follow so I don't need to know what's legal but what will work.

Nope... need a vent on your sink and shower, for sure!

Check to see if you can use mechanical vents (called AAVs). If you can use an AAV you can use the sink drain/vent to wet vent the shower and the toilet.

Let me know more and I'll post a drawing showing you what I mean, OK?

Mark

Good thing to remember, If a fixture has a trap it MUST be vented, Good luck, Tom