Basement Bathroom New Shower Vent Question

[Chesterhandyman]

Hey guys Ive been thinking of adding a shower in my basement bathroom. I have a toilet coming right off the main 4" drain. The 4" IRON comes out of the floor into 3" PVC and goes up to the roof. Im thinking of replacing the old iron toilet elbow with a new PVC 3"x3"x2" and running with 2" PVC to the new Ptrap for the shower.


My understanding is the 2" PVC run can be no longer then 5 feet for the main 3" stack to act as a vent.


My question is

1) Is the 5' measurement for venting from the main drain or from where the 2" pipe starts (off the new toilet elbow location)

2) If this doesnt work any ideas?


I added a picture to help with all the info i could think of, spent more time on it then expected

 

[Jadnashua]

Your shower drain is not vented and will be siphoned dry by the toilet.

 

[Sponsor]

 

[Chesterhandyman]

well darn, thanks for the response i guess i have to run a 1.5 inch pipe past and back up then connect it to the stack or to the roof?
thanks again

 

[hj]

You CANNOT connect it back to the stack, unless you do it at least 42" above ANY OTHER fixture connections above it. and since it will also be venting the toilet, (it is NOT vented now), it should be 2".

 

[Chesterhandyman]

ok thanks again man gonna have to take a look this def complicates the matter might have to dare i say "call a plumber"

 

[Jadnashua]

You might get by without venting the toilet, but, you DO need to vent the shower. That would only require a 1.5" vent line, I think, bigger if you want to (are required to) also vent the toilet.