Do I need more venting? Bathroom remodel

[Geoff Rhodes]

I am remodeling my bathroom, and I have run into a venting issue (maybe?). My original plumbing was all copper with soldered brass joints, and was laid out as shown in this picture:

https://photos.app.goo.gl/RJzD8qtoRF42YRcn6

There were no auxiliary vents leading from the sink or shower back to the roof vent.

The toilet and roof vent are 3in copper with soldered brass joints. I took out the sink and shower drains to rearrange where the fixtures are located/update things, and was wondering if I need to add auxiliary venting for those fixtures. Because of the framing/vent placement in the bathroom, I wouldn't be able to tie back into the roof vent, but I could add an AAV with a recessed box to access from an adjoining room.

Is add more venting necessary or beneficial? Do I need to tie in the shower and the sink to the AAV, or just one? The plumbing seemed to work properly (as far as I could tell) before I started the remodel.

 

[wwhitney]

Michigan is on the IPC per up.codes.

For a bathroom group (shower/sink/toilet in this case) you only need a single dry vent, which can wet vent the other two fixtures. However, the lavatory trap is higher than the shower trap or the toilet drain, so you can't use a dry vented toilet or shower to wet vent the lavatory.

Also, are you sure that the left hand vertical line in your drawing is a vent, and not a drain receiving drainage from the upstairs bathroom? If it's the latter, then currently you have no venting for the downstairs bathroom. (Wet venting is only for fixtures on the same story.)

The upshot, then, is that you need at least one dry vent for the downstairs bathroom; that could be the existing vertical line in your drawing, if it is a dry vent; or it could be a new dry vent you run up through the second floor and connect to the upstairs bathroom vent; or it could be an AAV.

And that dry vent should connect to the lavatory, where it can wet vent both the toilet and the shower. Or if connects to the toilet or shower, it can wet vent the other fixture at that level, but a separate vent is required for the lavatory. Which again could be any of the three options. [But again with the fixtures in the order shown, that lavatory vent could itself wet vent the toilet and shower, rendering the other dry vent unnecessary.]

Cheers, Wayne

 

[Sponsor]

 

[Geoff Rhodes]

Perfect, thank you for that clear explanation. You are correct, what I have labeled as a vent does receive drainage from upstairs. I will put an AAV in as a dry vent off the lavatory. Thanks!