Tricky Bathroom Drain Layout

[ScottyDee]

Hello everyone,

This is my first time posting and would like some help with a very tricky 2nd floor plumbing layout. I would like to take a week off of work and tackle this project. There are two bathrooms upstairs that are split between the toilets and showers. I have 9 and a half foot tall ceilings and will be doing a drop ceiling to make room for the drains. All of the cast iron has been removed and I sistered all the 2x10 joists (they were cut out with large holes where the 4 inch cast iron used to be)

The closest toilet is within 6 feet from the 4" stack so i'm assuming this will be okay
The closest shower is within 5 feet from the 4" stack

There is not much room to add vertical vents so i would like to do this with a horizontal layout if possible utilizing the main 4" vent and the 2" vent

Please feel free to make any additions, changes, or a new layout if this doesn't work

Attached is the layout I came up with after some brainstorming for a few days.
1) Will this layout work?
2) Is the 2 inch vent sufficient for this layout (this is the largest i can go)
3) does it matter which ties into the main 4" stack first (toilets vs showers)
4) Will there be any issues with the 2x2x2 wye that ties the showers & toilets to the vent (water draining from upstairs vanity)
5) Is the closest shower okay, or do i somehow need to get a vent in between the closest shower and the 4' stack)?
6) Would it make more sense to just branch off from the 4" horizontal run to the 2" showers than have a separate connection to the stack

 

[ScottyDee]

Any input would be greatly appreciated

 

[Sponsor]

 

[James Henry]

Draw a floor plan.

 

[ScottyDee]

Draw a floor plan.

Floor plan has been attached, I added vent locations. I also updated the original picture to include labeling and the second vanity

This will be a brand new layout, all of the original drains have been removed and PVC will be used. Let me know if you have any questions. Thanks!

 

[James Henry]

If your planning on just using the far left lavatory as a wet vent, this should suffice. A single wet vent can accommodate 2 bathroom groups and the fixture to wet vent connection is considered the fixture to vent distance. CHECK YOUR CODE BEFORE YOU DO ANYTHING.

 

[Mr tee]

If the 4" stack is a vent for a fixture(s) on the first floor it is not legal to use it for a second floor drain.

 

[James Henry]

If the 4" stack is a vent for a fixture(s) on the first floor it is not legal to use it for a second floor drain.

You are correct. He needs to sort that out.

 

[ScottyDee]

If the 4" stack is a vent for a fixture(s) on the first floor it is not legal to use it for a second floor drain.

Would the use of air admittance valves on the first floor remedy this? I can add one to the shower drain and vanity drain. Would I need an additional AAV for the toilet? It’s located a couple feet from the main stack with a 4 inch wye. Thanks! I will add a floor plan and sketch of the layout Of the first floor on my lunch break

I attached the first floor plan with aavs to the original post. Will these AAV's work?

 

[ScottyDee]

If your planning on just using the far left lavatory as a wet vent, this should suffice. A single wet vent can accommodate 2 bathroom groups and the fixture to wet vent connection is considered the fixture to vent distance. CHECK YOUR CODE BEFORE YOU DO ANYTHING.

Thank you very much. This really simplifies things for me

 

[James Henry]

Thank you very much. This really simplifies things for me

After the first shower you must transition to 3" drain then after the second toilet you could go to 4" depends on your code.

 

[ScottyDee]

-

 

[Mr tee]

The approval of AAVs depends on where you are. However, they only protect traps from negative air pressure and the danger in your situation is possible positive pressure so they would be ineffective.

 

[ScottyDee]

After the first shower you must transition to 3" drain then after the second toilet you could go to 4" depends on your code.

James after looking more closely at your picture and description i think this is the layout you are describing. Let me know if i'm wrong. Thanks!

 

[James Henry]

There are problems with the first floor plumbing, are you able to reroute the drains and vents? If not the second story plumbing won't fly.

 

[ScottyDee]

There are problems with the first floor plumbing, are you able to reroute the drains and vents? If not the second story plumbing won't fly.

The approval of AAVs depends on where you are. However, they only protect traps from negative air pressure and the danger in your situation is possible positive pressure so they would be ineffective.

I am able to run a vent pipe vertically, parallel to the main 4 inch stack and can tie it back in above all the second floor fixtures. Will something like this work?

 

[James Henry]

This would be the best solution but I don't know what I have to work with.

 

[ScottyDee]

This would be the best solution but I don't know what I have to work with.

the upstairs would be vented with both the 4 inch pipe that goes through the roof on the right side of the picture and the 2 inch vent that goes through the roof on the left side of the picture. Will the 2 inch vent that goes through the roof eliminate the need to run additional venting for the first floor?