Requesting review of mechanical vents for new 2nd floor bathroom - with photos

I am trying to add a second bathroom to my house without adding a vent through the roof. The 1 and only existing bath on other corner of house has a vent through roof. I want to connect to drains in basement, so have shower, toilet, sink, joining together in 3" drain, then dropping vertically for 8 ft to get to the basement. My worry was adding the shower downstream from the toilet that it would put positive pressure on the shower P trap when the toilet flushed and the slug of water was approaching the shower Tee. I added a AAV (mechanical valve) to the shower after the P trap so it wouldn't suck dry. Was going to do heel inlet on the 3" elbow below the toilet, but worried about backflow..

thoughts, suggests? Is this good as is? I'm ready to glue it.




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photos showing vanity into toilet drain, then shower into 3", with additional mechanical vent between shower P trap and 3" main drain.

 

I cannot see in your photo where the vents are.

We would not be allowed to use an AAV for a build where a proper vent could be installed on a new build such as yours.

If you had to use AAV's, you should still follow the basic rules for venting. The shower vent must be in the trap arm of the shower drain, and it must rise vertically to a point no less than 42" above the floor. If the WC is being wet vented through the sink vent, that vent should follow the same rule. The AAV's can be in the walls, but they must be left accessible by way of an access or vent cover.

 

Thanks for taking a look. I reconfigured the shower drain so it goes right to the AAV vent pipe, then turns a 180 and flows into the 3" toilet drain. Photos from yesterday's install

 

Thanks Terry for the note. The shower AAV goes up 42" into the new wall I built as shown in early thumbnail photo. Yes, sink cabinet has P trap into vertical pipe with AAV on top.

thanks!