Hi everyone,
I was looking around on the forums and am still not sure about a couple of things. I was planning on adding a basement bathroom and relocating my current 4" stack from 4 feet away from the wall to right up against the wall. That part will be easy I think. The challenge is for venting the bathtub and toilet. They would be dumping into a 4 inch horizontal underground sewer line (that the stack dumps into that has everything upstream see attached pics). Both fixtures would be less than the critical distance from the stack for venting purposes. BUT, I read on another forum that if there are upstream bathrooms and such I cannot use the sewer line as a drain AND wet vent. If that's correct then do I need to vent the toilet AND bathtub or just the bathtub. In my picture of the PLANNED dwv I have a bathtub on the left and toilet on right. I will be putting a wall between the two and water supply for tub filler and shower on the left side. This wall COULD also house a vent for the bathtub if needed. Could the vent simply come up vertically from the horizontal 4" sewer line (at the 90 turn towards the stack for example?) with 4-4-2 combo. That's all I can think of for now. If the whole idea is incorrect, please let me know. Any other suggestions are also appreciated.
PS a sink will also be placed opposite from the tub and toilet and will vent into the stack above the 3" input where the 2" dry vent takes off.
Many thanks in advance!
Regards,
Stevan

Before I can comment I'll need the drainage layout for the one and a half bath you're planing. Yes, you will have to run a vent on the tub. You are discharging a major fixture past a unvented minor one and that's a no-no.
Regards, tom

Hi Tom,
Sorry for the confusion and thanks for the quick reply! The 1.5 bath has already been finished prior to my arrival and is vented and dumps into the 3" pvc shown in the diagram, which subsequently dumps into the 4" stack in the basement. The vent for the 1.5 bath is separate from the vent in my diagram which takes off from the stack, so that should be all right. I'm only wondering about the new addition in the basement. So the toilet does not need a vent as drawn? The tub vent can be situated in the wall I talked about, before it dumps into the 4" horizontal sewer line? Thanks a LOT again.
Best regards,
Stevan

Hey Stevan,

Looks like you have things pretty much under control. Good luck, Tom

You're the best Tom, thanks again!