Rough in layout advice

[polymath]

I'm planning a rough in for a bathroom that will include the relocation of the laundry.

Any advice on which is the better plan and what may still be incorrect would be greatly appreciated.

Plan 1: I think this one is not code because of lack of vent for the floor drain. Am I correct in this assessment?


Plan 2: I think this one fixes the floor drain vent issue by wet venting it through the lav sink vent. But does it introduce a new issue with toilet venting since it cannot wet vent the laundry stack?
Do I need to add a 3x3x2 wye vertically in between the laundry 3x3x2 wye & and the toilet 90 running the vent up the wall to the AAV to individually vent the toilet?


Thanks in advance.

 

[Cacher_Chick]

You would not be allowed to wet vent the water closet through the laundry.

The wet vent of the shower through the lavatory should be all 2" pipe. Using bigger pipe reduces the scouring effect that the lav has on the pipe.

I would make the bath all one branch wet venting through the lav, and run the laundry and kitchen on the other branch.

There would need to be great deal of justification here for why a proper vent stack cannot be installed.

 

[Sponsor]

 

[polymath]

Thanks for your feedback cacher_chick.

I would make the bath all one branch wet venting through the lav, and run the laundry and kitchen on the other branch.

Am I correct in thinking your suggestion translates to something like this?



I think this plan still has issues because of a lack of a floor drain vent. Am I correct in this assessment?

There would need to be great deal of justification here for why a proper vent stack cannot be installed.

The existing 1.5 inch stack would need to upgraded to at least 2" and the basement vent would need to connect at least 6" above the flood plane of the kitchen sink. This would require at least opening the kitchen, and a bedroom wall and most likely opening the 1st floor ceiling joist past code for a load bearing wall.

 

[Cacher_Chick]

That is what I was suggesting. We can wet vent a bath group, but other fixtures may not share the wet vent.

If the house is stick built, we would drill through the top and bottom plates of an interior wall for the 2" vent, and then go through the roof or tie into another vent through roof in the attic. In a single story house with 8 foot ceilings, one stick of pipe goes down through a 2x4 stud wall cavity without compromising anything.

 

[polymath]

While that most recent design works for wet venting the toilet through the lav sink, the floor drain is too far downstream to be wet vented. That's why I thought I needed the 3" pipe between the lav sink & floor drain in the earlier plan where I kept the toilet downstream of the floor drain (Plan 2). I now know that plan 2 fails for lack of toilet vent but I could individually vent it up the wall behind the fixture, with a 3x3x2 wye & a 1/8 bend. Am I correct in these assessments?
View attachment 23030

The house is a stick built bungalow. To accomplish what you are describing would probably require opening the upstairs bed room wall at the ceiling to access the top plate. It cannot be accessed from the attic, maybe the roof though. It would definitely require a hole in the either the kitchen wall or the upstairs bedroom for access to the top/bottom plate of the 1st/2nd floors & to branch to the basement vent.

While I understand the traditional vent is better, this seems awfully invasive when an AAV is allowed by code in Michigan. When I gut the kitchen sometime in the future it would be way easier to run a new vent.

Thanks again for you help with this.

 

[Cacher_Chick]

There are options for the floor drain vent, some of which depends on where the walls will be and the direction of the overhead floor joists. IMO, there should be a 2" floor drain in both the laundry and and the bath, which I would center off the fixtures.
With your old work, some consideration has to be made for the condition/flatness of any existing floor with regards to positioning the drain.

 

[polymath]

Yes, the location of the laundry floor drain is a problem without a great solution. It's further away from the appliances than I would ideally like. This was an issue with the original location of the appliances as well as the new. The floor pitches pretty aggressively towards the drain's current location, so moving it would require removing a pretty significant section of the floor.

The venting issues are the drain is in the middle of a room, not close to any walls. Its downstream plumbing does not run anywhere close to a wall until it exits the house about 20' away. Since I cannot run a horizontal dry vent below grade my only option is venting through upstream plumbing where it crosses a wall 6' 6" away.

 

[polymath]

Thanks again cacher_chick for your feedback so far, it has been a big help.
I think I've finally come up with a solution that solves the floor drain issue and groups the bath group properly.

In this layout by rolling that first 3x3x3 wye 45 degrees it elevates the kitchen and laundry branch enough that I can attach the laundry floor drain to that branch. Then I can add an individual vent in the new wall that will enclose the existing kitchen drain.

Any additional feedback would be greatly appreciated. Thanks in advance.