Toilet Trap Distance and How To Vent Help Please

[ARC]

Hello. My situation is that I'm remodeling a 100-year old bathroom (78" x 90") were all the current plumbing/venting is on the right-hand side. I'd like to move the toilet to the left-hand side, which will actually put fixture spacing more in code and allow for a larger vanity sink. I'm in Minnesota a the code is UPC. Here is the problem:

The closet flange trap distance to connect to the main stack will be about 7'12" give or take. I know the UPC says 6' max, and IPC say unlimited for trap arm to vent. I was going to use 4" pipe instead of 3" since that is the current connection to the stack anyway. I'd prefer it if I could just run this and not add a 2" vent pipe, but I'm happy to be told this is a horrible idea.

I would just run the 2" vent pipe per UPC code if it were that simple in this old house, but the left wall tops out in a dormer of a finished attic. The joists were 2x6 and doubled to make code at the time by the contractor. It's close enough to the knee wall that I'd only have to go through one set of joists. But I can't just drill a 2.5" hole in 2x6 and meet code there either since it's more than a third of the joist and closer than 2" from the top or the bottom. If I do this I could block on either side of the cut joist to the joist on either side to reinforce, but this is a lot of work. Last, if I do vent and cut the joist this would put me near the main metal stack. I could get there with a couple of 90˚ turns.

The shower and sink will tie into existing venting that I assume must tie into the main stack as there isn't other vents coming out of the roof, but haven't demoed that yet to confirm.

Questions:

1) Besides adhering to the code, should I worry that this is too far away for the trap run? I know a bit about the debate about toilets self siphoning. I don't plan to sell my house anytime soon and this is by far the easier solution. Not sure if the UPC is outdated or the IPC is on this toilet vent issue.

2) If I do cut the into the double top plate, into one doubled 2x6 joist and box frame it for support is this a good solution? Does anyone have experience on this?

3) Does the 2" vent pipe have to be tied into the main stack or can I just pop it out the roof? This seems much easier than cutting the main old stack, especially since it's near the roof and I have no idea how it's supported onto the fraining, if at all.

Thanks for any help and suggestions.

 

[Terry]

How about a picture showing what we are looking at with some dimensions? Can be uploaded as an attachment 800 pixels or less.

A 2" vent through the roof will handle the entire bathroom.

 

[Sponsor]

 

[ARC]

Thank you Terry for the speedy reply. The 2" answer was surprisingly difficult to find online.

I hope these photos help and are in order from the finished attic bedroom to the main floor bathroom to the basement. I put a couple of pieces of wood to represent approximately where the joists are located, and a coupling to where I believe the 2" vent would pop out of the double plate if I went directly up from the toilet in the wall. You can ss it's not a long way to get behind the knee wall

The bathroom pics you can see where I placed a new PVC flange for the toilet, and where the old one was (it was only 14" from the sidewall)

For the basement pics you can see the main stack with the old toilet drainage. In the further view on the top left you can a circle in black sharpie where approximately the new toilet drain would go. With slowly taking over a couple of feet with 45˚.

Come to think of it I guess I'll have to run a 3x3x2" wye to get the vent over to the wall cavity. in the opposite direction I need to drainage to go. Does that make sense? I assume I have to go at an angle with the 2" and through the 9.25" first-floor joists until I can go verticle unless someone has a better idea.

Thanks for the advice. Trying to upgrade this before my girlfriend and her daughter move in and permanently lost my job due to Covid so trying to save money here. I'm handy enough so feel capable of doing the work if I how to exactly resolve these issues.

 

[Terry]

I would consider cutting the cast below the fitting for the bathroom and using a santee, head over toward the wall with the window with 3" and picking up the toilet with a combo and then run 2"over to the lav and tub.
The 2" only needs to go as far as the 2" combo for the lav and then the tub can use 1.5".
The wet portion of the lav is 2" and the vent can reduce to 1.5" and then tie back into the main stack.

 

[ARC]

Wow. Thanks for drawing that up to clarify. The layout is what I was shooting for and I will make some built-in storage by the back of the tub/wall. I was thinking to do a 30" lav so as to have about 28" for a towel bar between lav and shower. I'd prefer a 36 but have no idea where to hang towels then.

FYI: I do not believe that the old tub or shower vent anywhere other than into the wall. I'll know when I demo that part of the wall to tile, but I ran a wiring fishing tool along the side they would have connected to the stack and did feel a santee connection for them. There is nowhere else they could vent to.

So then 3 subjects for questions in this situation you so kindly drew up. I'll try to have these be my last. Thanks for helping and I really appreciate you Terry.

1) The main thing I wonder is part of my original inquiry which is that the dwv from the toilet flange to now the lowered wet vent 3" combo long turn wye is still a bit longer than 6'. I'm measuring around 66" horizontal plus around 16" drop. Are you saying just not to worry about it not being code since it will be fine? Or are you saying your layout is code for UPC?

2) The stack center is about 15.5" from the tile. Isn't that where the dwv for the lav should go? So then should I cut more out to add a santee for the lav directly into the stack? I don't think the stack is supported at all so I assume I should add a stack clamp in the knee wall in the attic, right? Basically given that I'd like to cut it higher as it also sticks out of the wall at a female connection, doesn't it make sense to cut it from below the fitting all the way to the knee wall where I have access and replace it all?

3) Lastly, if I do need to vent it on the left wall behind the toilet to be code and I use a long turn wye horizontally, instead of putting the cleanout in the back, could I extend it sloped up steam and use a santee to get the vent more in line with the wall and put the cleanout there instead? I guess technically that dead-end 3" section would be close to vertical but as you see the existing stack fitting top is only 1.5" below the joist. After pitch this doesn't leave me enough hight to run the 2" at 45˚ to the wall cavity.

Thanks again