Regarding the rule about no minor fixture downstream from a major one... Is there a point at which it's so far downstream that this rule does not apply? In my plans, I have a WC on the second floor that drains into a branch which passes underneath a kitchen sink on the first floor. Can I connect the sink to that branch (in the basement), or do I need to create a new branch for the sink? I assume the answer to this is new branch, but thought I'd at least see if there's a way to avoid it.

Thanks.

David

Yes, you may connect to the branch if you vent the sink.
The rule is, A major fixture may not be dischared past a UNVENTED minor one.
You may connect the sink anywhere you like as long as you vent it.
EVERY fixture that has a trap MUST have a vent. Good luck, Tom