What to do with drain vent?

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asmad

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I am in the midst of demo for a bathroom remodel and, long story short, need to convert existing 1.5" drain to a 2" drain. The vent for this drain takes three turns into an exterior wall, up into an inaccessible eave and then back across the attic space toward the direction it came from the floor below. I'm not sure why it took the three turns instead of going straight up unless it is because the electrician got there before the plumber did, if that would be a reason, because there is a single electric line going across the wall above the vent where it turns.

So I have a few options.
1. convert to 2" WHERE POSSIBLE, though this probably means leaving the elbows in the eave at 1.5"
2. run a NEW vent without removing the original vent
3. run a NEW vent and bypass the old vent.
 

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asmad

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Sorry, didn't finish.
So what to do?
Or can I just replace the drain and leave the vent alone?
And do I need to replace the drain all the way to and including the T to/on the waste line?

By the way, this is for a wet zone area, clawfoot tub draining onto a large shower floor. I have been in the John Bridge forum for a while and this was suggested. Total GPM in the range of 7.5-8.5, essentially both a tub and shower going into the same drain.
 
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hj

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1. If I had installed it originally and an electrician ran a wire across in the middle of the wall, (which they ALWAYS do, I think they take a class on how to run single wires and block the space for anyone else), it WOULD have been "rerouted" or removed.
2. The vent size is NOT tied to the drain size so you probably do not have to change ANYTHING other than the drain line.
 

asmad

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That would be fantastic. After my post, I checked chapter 9 of the IPC and I think table 906.1 confirms I am ok with the 1.5".
 

asmad

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I got the existing tub drain partly excavated this morning, just enough to see what's what. Due to the depth and the length the trap jogs over under the slab, I don't have a line of sight to the part of the vent stack where the trap meets it, but I can get a camera down in there and snapped this picture. A few things concern me...
Firstly, I think I will have no room to cut anything unless I jackhammer up the slab a bit. As indicated on the picture, the far side of the stack is only about 12" from the edge of the foundation. Is it still safe to take out that wedge of slab marked in blue? Or should I try to cut the drain without doing that by excavating as much dirt as possible? (which may be just as problematic to a foundation?)
And I've usually cut pipe with a hacksaw. I'm sure I'll need something smaller. Anyone have good luck with something that will cut in tight spaces?
Additionally, I'm going from a 1.5" drain on a 1.5" stack to a 2" drain on a 1.5" stack. Given that, can I do a reducer BEFORE THE TEE connecting the trap with the stack? Or do I HAVE to cut the tee of the stack out and replace it too? I figured I could do a reducer before the tee since it's reducing there anyway but wanted to get some feedback.
 

asmad

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Sorry, I guess I should actually post the images...
 

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asmad

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Since I last posted (see above TWO, both mine) I have learned two things...

The first is that the waste line runs right back by that trap. I wonder if I have the option to tee into that waste line and run up a new section of the vent. It would mean any slab demo would be more in front of the drain instead of to the left, close to the edge of the foundation.

THEN I realized that the drain actually transitions to 2" before the trap!
So I think given these two things, I definitely don't have to replace the T on the vent stack... just replace things over from there to the new 2" drain.

Thoughts?
 

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asmad

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It's been a few hours, so I'm just checking back. Might be slow here on a holiday weekend. :) But for me, this is work time. I wanted to see if this helps clarify what I am asking. I can either remove the existing drain and cap it off - or actually utilize the existing drain and add a second drain... both in somewhat this configuration. White is existing in the drawing, yellow is what I would add or use to replace. I also don't know if I really need that part going up to join the vent stack because the trap would only be about 14" away from it to begin with. At this point, I'm hoping to get what I need to do this job in the morning, so any replies would be appreciated. Or should I create a new thread with a new title so that my current part of the project is better communicated? Thanks.
 

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Reach4

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Concept in your drawing looks good to me. I am not a plumber. I know that you will need to pay attention to the fittings too. I think that fitting near the E in WASTE would be a long sweep combination wye. https://terrylove.com/forums/index.php?threads/santee-vs-combo.37658/ note that the fitting by the word VENT should not be a sanitary tee either.

You will also need to pay attention to pipe sizes. I think the drain below the new santee should be 2 inch (I think) and the vent above will be 1.5 or larger.
 
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asmad

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Good point about the type of fittings. I checked out that link you provided, but it looked like a bunch of bickering and I'm not sure where everyone landed. ;)
FYI, here is how that area looks on that vertical to horizontal bend of the vent...
 

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Reach4

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You should do more searching. The long sweep combo fitting I think everybody agreed on.
 
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