New basement bathroom & venting

[James Feger]

Hello all,
I have been reading through the forums, the IRC, and the IPC. I am now adequately mixed up and looking for some sanity. . I am adding a new rough-in for a bathroom (Lav, WC, Shower) in my basement. I am going to tie into an existing 3" main off of a stack that heads to the street. My main question is related to proper venting, and what, if any, the venting provided by the 3" stack provides. Originally I was thinking I had to vent each fixture, then I read about DFU's, and wet-venting. I believe I am down to two options:

1. The 3" stack that heads up from the basement, through the 1st and 2nd floor, and out the roof provide the venting I need. (I hope, but I am sure I am missing something)

2. I can wet-vent off of the lav with an AAV into the unfinished side of the wall and that provides proper venting for the lav, the WC, and the shower. I understand the floor drain doesnt need a dedicated vent if its to be used for overflow/spill and not a dedicated true drain.

After the venting discussion, I also want to know if the lav must drop below slab as the diagram shows or if I can run the waste pipe horizontal in the wall and then 90 down to the 3" below slab. I ask because I have already jacked out the floor over the 3" line, and was hopeful I was close to done with that part of the work.

 

[Tuttles Revenge]

No code I'm aware lets you drain plumbing from another floor or another set of bathrooms on the same floor through the middle of your wet vent. It looks fine otherwise.. tie the upstairs in where the black arrow is.

 

[Sponsor]

 

[James Feger]

Hi @Tuttles Revenge ,
Thank you for the reply. I should clarify. The 3" stack is existing and as built in 2011 has the 2nd floor full bath, and the 1st floor kitchen sink and dishwasher.

If I read what you are saying though, I cant use that as a wet-vent for the newly created bathroom setup in the basement, so I will need to vent somehow down there. Therefore, my wet vent setup off of the lav is correct for the WC and the shower?

 

[wwhitney]

An AAV for the lav can wet vent the WC, shower, and floor drain, if no other fixtures drain through the wet vent. So your drawing would be OK if the 3" stack were deleted.

Of course, you still need to connect the 3" stack to the sewer. You just can't do it between the lav and the WC, if you want the lav to wet vent the WC, shower and flood drain. The 3" stack would need to come in downstream of all the wet vented fixtures.

Cheers, Wayne

 

[James Feger]

Ah.... ok, thank you @wwhitney . So, what I have here indeed does not work as drawn. I think I have two options in this case.

1: Individual dry vent for each fixture
2: Bury a parallel 3" pipe as the branch for the Lav, WC, and shower, wet vent as designed, and wye into the main line downstream.

Of the two options, option 1 seems to be the best / easiest in terms of work effort for result. Ill redo my diagram with what I am thinking. I believe if its a dry-went, the WC and the shower can tie into the same pipe using a common AAV if the pipe is 2", correct?

 

[wwhitney]

(2) is likely best. Note that under the IPC, your dry vents have to be vertical (at least 45 degrees above level) until 6" above the flood rim level. And the dry vent takeoff has to be on the fixture drain, before the drain joins any other drain. So I don't see how you can do (1) with the 3" drain where it is.

A picture of the existing conditions and proposed layout might help us advise you.

Cheers, Wayne

 

[James Feger]

Ok. I think this is what option 1 of dry venting looks like. The stack from the upper floors is still in the same place, I still connect into the 3" main out to the street, but now each fixture has a dedicated vent. Does this work in your assessment? Also, any thought on the Lav drain pipe going horizontal (sloped) in the wall then dumping down at 90 into the 3" versus going below slab immediately and then going horizontal under ground?

Thanks again!

 

[wwhitney]

Dry vent takeoffs need to be vertical (at least 45 degrees above level) and stay vertical until 6" above the flood rim level of the fixture. No horizontal dry vents below the slab.

Cheers, Wayne

 

[James Feger]

Hi Wayne, thank you. Im at a loss at the moment then. When the software designed the vent connections horizontal off of the main drain pipe, I thought it would be problematic, but was hopeful it will work. Im at a loss as to how to properly route the pipes within the dirt below the bathroom since there isn't a wall to go directly vertical into. I *might* be able to pickup a wall downstream in the bathroom on the other side of the shower, but that will be pushing the 6 foot limit as the pipe runs for the WC.

Curiously, the original rough-in for the house is tied into this same drain pipe downstream near where the black arrow in my original picture is. I dont see dedicated vents, which led me to think it was setup as a wet-vent off of the LAV as in my original design. All good, except it would still get the suction pressure from the flow of the stack passing by.

If I am within the 6' as the pipe-flys would the attached work? Its hard to see in the 3d render, but that vent stack going into the wall is vertical with a combo-wye fitting off of the 3" sewer pipe under slab

If not, I will likely go a bit more drastic and pickup the 3" main sewer pipe further downstream with the fixtures so I can deliberately run under the walls.

 

[wwhitney]

How about something like the layout below?

I'm assuming that the wide green line is an existing underslab drain line. I show the (red) lav drain crossing over the existing underslab in the wall; depending on the depth of the existing, you could cross over under the slab, and then your new parallel 3" line would have to drop down a little at the end.

This doesn't pick up the floor drain, but depending on the bigger picture, that might be OK, or it might be better to extend the parallel 3" line down the page to pick up the floor drain. Some more information on the type of floor drain and whether it is existing would help.

Cheers, Wayne

 

[Tuttles Revenge]

I came up with the same basic idea as Wayne, just a slightly different layout.

 

[James Feger]

Hi @wwhitney and @Tuttles Revenge I really appreciate it. I also noticed I missed the previous note Wayne shared about the placement of the dry. The two different options you both shared indeed makes sense and the lightbulb lit up for me on what my basic challenge was with "non local" fixtures draining through the wet vent.

It appears I will be doing a lot more jack hammering and digging than I had hoped, but such is life to make sure its properly done.

As for the floor drain, it will be a new addition. I thought I had read that it didn't need a dedicated vent if it was simply for overflow / emergency. However, since I will be running so much new piping, I will attempt to tie it into the newly placed 3" line so it can wet-vent off of the lav also.

Thanks again!

 

[wwhitney]

So what is your plan for keeping the floor drain trap from drying out, letting sewer gas into the basement? A trap primer?

Cheers, Wayne

 

[James Feger]

Hi Wayne,
Yeah, I had thought about that or typical maintenance dump of water. Is there a suggestion other than that?

 

[James Henry]

Contractors are starting to use plastic trap seals to save money. Their spring loaded to let water in but not sewer gas out.

 

[James Feger]

Contractors are starting to use plastic trap seals to save money. Their spring loaded to let water in but not sewer gas out.

Ill have to check those out, thank you.

 

[James Feger]

Ok team, I redid the render in the software and I think I have accurately captured the suggested approach.
The shower looks like a tee, but it's not.

I really appreciate the input and guidance, you guys are the best!

 

[wwhitney]

Looks good for the IPC. If the lav is in a vanity cabinet, it might be easier/nicer to place the AAV there than in a wall box, but either way is fine.

Cheers, Wayne

 

[James Feger]

Looks good for the IPC. If the lav is in a vanity cabinet, it might be easier/nicer to place the AAV there than in a wall box, but either way is fine.

Cheers, Wayne

Thank you Wayne! I'll make a game-time decision on that. The half-stack will be "in the wall", but the backside of the wall is in an unfinished part of the basement that will be used for storage. No real issue as far as I am concerned either way. Much appreciated!!

 

[James Feger]

(EDIT Update: I decided to run its own trap and line in concept with the pictures above. I have taken multiple pictures of my puzzle-masterpiece. . Im going to post up here shortly for feedback and confirmation it looks good to code. Nothing is welded/glued in place yet.

Hi @wwhitney and @Tuttles Revenge (or anyone who knows!) I am now in the build phase and have run into another question. Is there an issue with running the floor drain into the downpipe between the shower and above/before the p-trap? Id use a san-tee above the p-trap effectively creating a shared p-trap for the two drains (shower and floor drain). (Slope, direction all accounted for obviously). This is all 2" pipe before hitting the main 3" pipe. The distance from the floor drain to where the san-tee would be is ~24" or less. The trap arm I can make anywhere from 4" to 12" without issue before it hits the wye to tie into the 3" main

PS - Tapping into the 3" main pipe was more challenging than I expected as there was no wiggle in either side of the pipe once I cut an opening for the wye to tie in. I ended up going with the 3005-33 fernco (full metal jacket) and getting it all back together that way. All seems good and the slope / flow all seems solid (no pun intended). Thanks again!