Stacked washrooms sharing stack

[Plumber69]

Can I simply just tied into the soil stack on the upper floor to add a sink and toilet. There is a bathroom below. Can both bathrooms share a stack

 

[Terry]

There is no wet venting between floors. Once it's a vent, it stays a vent.

 

[Sponsor]

 

[Plumber69]

There is no wet venting between floors. Once it's a vent, it stays a vent.

Hmm I could run a 2 inch vent from the lower bathroom to attic. Replumb some of the lower bathrooms plumbing

There is no wet venting between floors. Once it's a vent, it stays a vent.

I can disconnect the 4 inch vent stack and tie into the main sewer. Then run a 2 inch vent from from that connection to attic. My only problem with doing this is the bathroom sink in the lower bathroom will still be tied in the 4 inch stack which will now be the main drain for the upper bathroom

 

[Terry]

My only problem with doing this is the bathroom sink in the lower bathroom will still be tied in the 4 inch stack which will now be the main drain for the upper bathroom

If the lower lav is vented before it enters the main stack, then the problem is solved.