We are remodeling the bathroom, moving the sink and bathtub (originally a shower). The shower and toilet were along the same pipe line and vented in a privacy wall next to the toilet. The sink used and AAV.

I can continue to use AAV in the new sink location or tie all three into the same vent (if possible). All three walls that could be used for venting are structural walls and cannot be used for venting (as far as I know). The one internal wall has a triple joist beneath it so cannot be accessed directly.

Based on my image showing the placement of the sink, bathtub and toilet, along with the existing plumbing locations, what are my options for venting? Am I able to vent with just one vent? Will I need two separate vents? What locations are available to me that don't require the privacy wall? I figured the shower would have to be vented in the adjacent wall by the drain, but I'm unsure about the sink and toilet.

If I doubled the thickness of the wall behind the toilet (added another 2x4 wall) I could vent in that "false wall", but it would visually look odd having just that section twice as thick as the section on the other side of the door.

Any options and advice are welcome! Thanks!


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I would remove the AAV if possible. Traditional piped vents have no moving parts and is a quite reliable system vs a mechanical AAV which will eventually fail and need to be replaced. In your case I would run the sink's vent up the wall and then connect into the vent system above in the attic.

 

Since you have 2 separate drain lines, you'll need 2 separate vents (that can be tied together in the attic).

I agree that your best bet is through the outside wall by the vanity. That'll properly vent the toilet and vanity. But it depends where it ends up in the attic above and if you can access it. It might be possible to turn it into the joist cavity in the ceiling also if that helps.

I also agree that an AAV should only be used as a last resort. In many locales, they aren't allowed.

 

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I would but I don't have an attic. It is a vaulted ceiling with minimal space between the ceiling and roof.

Something I failed to mention is that this is a manufactured home and has a crawlspace which gives access to the plumbing. Does that change recommendations on how I might vent this?

 

Is the bathroom ceiling vaulted as well? Could the vent pipes be joined in the ceiling and then go out the roof as one?

 

Yes, it is vaulted. The space is very narrow. Large enough to fit a 2" pipe but no way to do the work without ripping down a good section of ceiling. Even if I were to do this, I have the following questions:

1. What would be the recommended location for venting the toilet and sink? In the wall by the sink?
2. Is the distance between the wall and the toilet within allowable distance (about 7.5')?
3. Is it safe to run a vent pipe through the outer wall? Placing a 2" pipe through the 3.5" space of 2x4s?

So, I guess the recommendation is to vent the tub via the inner adjoining wall and the sink+toilet via the outer sink wall. It just comes down to how the sink+toilet would tie together.