DWV layout help!

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Kevinjm4

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This already has existing waste and vent pipes installed (they haven’t poked through roof just yet thankfully), however as in an earlier thread they are most likely wrong. It contains two horizontal vents under the floor. I will also post a drawing to the best of my ability how they are currently laid out. I’m willing to fix before moving forward with my project.

I would prefer to vent only on the right wall, second option would be only the left wall, third and the “if necessary” option would be venting pipe going up both left and right walls. My concern basically is limiting roofing penetrations, but not opposed to 2 penetrations here if needed. Routing one of the vent pipes in the rafters MAY be an option but it’s a vaulted ceiling (no attic) so it’d have to be bored through the 2x6 roof rafters.

The 4x6 beam may be a problem. It is a lot easier to get around or to notch the bottom of it further down the room closer to the bottom/south wall...toward the main line/concrete footer. As a way to explain the height of the 4x6, it is under 2x6 joists, and parallel and at the same elevation as the 3” toilet drain line up until the concrete footer, which is where that same drain line drops fully below - in elevation - the beam. The 3” toilet drain may be able to be moved to the left side of the beam after checking my slope and amount of room down there)

Sorry for my iffy measurements in places (4’ or 5’) I don’t know EXACTLY (given p-trap, etc.) where the measurement needs to be taken from...

EDIT: 3” toilet drain can probably be routed onto the left side of the beam immediately after toilet flange
 

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Kevinjm4

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I think I see two options...
1) move 3” toilet drain to the other side of the beam so the tub can tie in to it in a shorter distance, as well as the shower, and have those wet vented in the toilets line. Have toilet vent, and tie into vanity vent and go up and out the roof.

2) leave it as is, vent up both left and right walls. Toilet and vanity tie together above flr, and shower, tub tie together above flr which would be two 2” vents poking through roof.

Both methods will include cutting out dry horizontal vents.

Do both of these work? One better than the other? Or another recommendation?
 

wwhitney

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The lav absolutely requires a dry vent in the right hand wall. A variant on option (2) would be simplest: make the lav a 2" drain and vent, use it to wet vent the WC, put a dry vent on the tub that rises into the left hand wall without going horizontal below the floor, and use it to wet vent the shower.

But if you absolutely want to avoid vents in both walls, you can do something like the diagram below. Red is 3", Blue is 2", Green is 1-1/2". [Edit: none of the drains are 1-1/2", that was an error and I updated the diagram. The lav dry vent can be 1-1/2".] The idea here is that the lavatory can wet vent the tub and the shower by crossing over the beam through a joist bay. If the shower and tub drains are below the joists, it's probably best for the lav drain to cross over the beam fairly low and then just gradually drop below the joists to join the tub drain.

The lav then wet vents the tub; with a 2" trap on the tub, the tub trap arm can be up to 60" in length, so that the maximum allowable run from the tub trap to the wye where it joins the lav (along with a 2" maximum drop). The combined drain goes on to join the shower and wet vent it, too.

That doesn't address the WC, so you route it under the joists near to the right hand wall to pull a 2" dry vent off it (with a combo, which could be rolled up to 45 degrees off vertical) that can rise up into the wall, within 6' of the closet flange, measured along the pipe. Within the wall the 2" WC dry vent and the 1-1/2" lav dry vent can join at a height at least 6" above the lav flood rim; if the distances work out, the two dry vents could be in the same stud bay, so you don't have to drill any studs (otherwise it would be easier to bring the 1-1/2" vent to the 2" vent, rather than vice versa).

I'm not sure exactly what's going on at the bottom of the page with the footer and the existing 3" drain, but you just connect your new 2" drain and new 3" WC drain to the existing 3" line however is required (everything is vented), either separately or by combining them first if that's easier.

Cheers, Wayne

image.jpg
 
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Kevinjm4

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The lav absolutely requires a dry vent in the right hand wall. A variant on option (2) would be simplest: make the lav a 2" drain and vent, use it to wet vent the WC, put a dry vent on the tub that rises into the left hand wall without going horizontal below the floor, and use it to wet vent the shower.

But if you absolutely want to avoid vents in both walls, you can do something like the diagram below. Red is 3", Blue is 2", Green is 1-1/2". [This assumes a single lavatory; if double (2 traps), change the 1-1/2" drain to 2"). The idea here is that the lavatory can wet vent the tub and the shower by crossing over the beam through a joist bay. If the shower and tub drains are below the joists, it's probably best for the lav drain to cross over the beam fairly low and then just gradually drop below the joists to join the tub drain.

The lav then wet vents the tub; with a 2" trap on the tub, the tub trap arm can be up to 60" in length, so that the maximum allowable run from the tub trap to the wye where it joins the lav (along with a 2" maximum drop). The combined drain goes on to join the shower and wet vent it, too.

That doesn't address the WC, so you route it under the joists near to the right hand wall to pull a 2" dry vent off it (with a combo, which could be rolled up to 45 degrees off vertical) that can rise up into the wall, within 6' of the closet flange, measured along the pipe. Within the wall the 2" WC dry vent and the 1-1/2" lav dry vent can join at a height at least 6" above the lav flood rim; if the distances work out, the two dry vents could be in the same stud bay, so you don't have to drill any studs (otherwise it would be easier to bring the 1-1/2" vent to the 2" vent, rather than vice versa).

I'm not sure exactly what's going on at the bottom of the page with the footer and the existing 3" drain, but you just connect your new 2" drain and new 3" WC drain to the existing 3" line however is required (everything is vented), either separately or by combining them first if that's easier.

Cheers, Wayne

View attachment 80735
Thank you for the reply! I have a few clarifying questions in response if you don’t mind.

Responding to your first option paragraph:
You mentioned using the tub to wet vent the shower. Is the shower close enough to the tub to be wet vented (I thought it was 5’ for 2” but that may be something else?)? Also, should the tub be a 2” drain and a 2” vent at that point?


General question about wet venting:
I was under the impression a wet vent needs to be downstream of the fixture it is venting through. I guess normally when I see a diagram the vent being used is usually the first one in the line, then the rest downstream wet vent back through it. (I’ll include a picture of what I’m talking about)
So for example in your illustration the tub using the 1.5” lav drain to wet vent. I’m having a hard time wrapping my mind around. Feel free to just say, “trust me, that’s wet vented”... but I am trying to gain a better understanding as well. Basically, is it equivalent, in a way, to what you have on the right side of the wall where the WC drain travels “downstream” a few feet then vents up/WC can travel 6’ before needing a vent.

With the 1.5” that crosses over, would it be better to make it a 2” / is it permissible?

The footer is presumably from the original perimeter of the house prior to the addition. There is also a roof under our roof in the attic, which also makes renovation that much more complicated
 

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wwhitney

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You mentioned using the tub to wet vent the shower. Is the shower close enough to the tub to be wet vented (I thought it was 5’ for 2” but that may be something else?)? Also, should the tub be a 2” drain and a 2” vent at that point?
The distance between the tub and the shower is immaterial for wet venting; it just determines the length of the wet vent, which is not regulated. What is regulated is the distance from a trap to its vent connection (the length of the trap arm), whether that vent connection is wet or dry.

So for the "tub is dry vented and wet vents the shower" scenario, if the tub has a 1-1/2" trap, then the trap arm is limited to 42" (and 1-1/2" maximum fall), i.e. the distance from the trap outlet to the branch connection of the "vertical" wye or combo that is the dry vent takeoff. And if the shower has a 2" trap, the trap arm is limited to 60", i.e. the distance from the trap outlet to the horizontal wye or combo connection where the tub drain comes in.

As to the last question, I prefer to do tubs with a 2" trap. But if you use a 1-1/2" trap, then you run into the requirement in the UPC that a 1-1/2" horizontal drain (other than a trap arm) can only carry 1 DFU, and a tub is 2 DFUs. If your tub drain turns downward when a dry vent comes off, i.e. you use a san-tee, then a vertical 1-1/2" drain can carry 2 DFUs, so your tub fixture drain can stay 1-1/2" until it either meets another fixture or turns back horizontal. But if your tub drain stay horizontal after the dry vent takeoff, you must enlarge the tub drain to 2" at that point. I.e. you could use a 2x1-1/2x1-1/2 combo for the vent takeoff.

So in the "tub horizontally wet vents the shower scenario" the wet vent is going to be 2", because both the normal rules for a tub drain, and the wet vent rules, preclude 1-1/2".

More to follow.

Cheers, Wayne
 

wwhitney

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I was under the impression a wet vent needs to be downstream of the fixture it is venting through.
With just 2 fixtures, A dry vented and wet venting B, there's no restriction, you just join A to B. And again, the distance from A's trap to A's dry vent takeoff is regulated, the distance from B's trap to A's drain joining B's drain is regulated, but the distance from A's dry vent takeoff to A's drain joining B's drain is not regulated.

With 3 fixtures, A dry vented and wet venting B and C, then it is not allowed to have drains B and C join, and then join A's drain for the wet vent. That's because you can't join unvented fixture drains, each drain needs to be vented before or as it joins another drain. So either A joins B, and then A+B joins C; or A joins C, and then A+C joins B.

And to be clear, it's the order of the drain connections that matters; the physical layout of the fixtures doesn't.

With the 1.5” that crosses over, would it be better to make it a 2” / is it permissible?
That was a mistake in my diagram that I went back and fixed, it's required to be 2". The IPC would allow 1-1/2" for a wet vent carrying only 1 DFU, but WA uses the UPC which requires all wet vents to be at least 2".

Cheers, Wayne
 

Kevinjm4

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With just 2 fixtures, A dry vented and wet venting B, there's no restriction, you just join A to B. And again, the distance from A's trap to A's dry vent takeoff is regulated, the distance from B's trap to A's drain joining B's drain is regulated, but the distance from A's dry vent takeoff to A's drain joining B's drain is not regulated.

With 3 fixtures, A dry vented and wet venting B and C, then it is not allowed to have drains B and C join, and then join A's drain for the wet vent. That's because you can't join unvented fixture drains, each drain needs to be vented before or as it joins another drain. So either A joins B, and then A+B joins C; or A joins C, and then A+C joins B.

And to be clear, it's the order of the drain connections that matters; the physical layout of the fixtures doesn't.


That was a mistake in my diagram that I went back and fixed, it's required to be 2". The IPC would allow 1-1/2" for a wet vent carrying only 1 DFU, but WA uses the UPC which requires all wet vents to be at least 2".

Cheers, Wayne
Wayne, when I go to remove those horizontal dry vents, is it permissible to simply cut it off at the beginning of the straight pipe right after the fitting and cap it, or do I need to remove it altogether like it was never there? I will include images with a red line indicating where I’d like to cap
 

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wwhitney

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If your system is plugged where the building drain exits the house, and all the fixtures are capped, and you filled it with water to the roof vent (a standard leak test for rough DWV plumbing), you want everything to empty when you unplug the building drain. So don't create dead ends that will hold water/sewage that are connected to live DWV.

Cheers, Wayne
 

Kevinjm4

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If your system is plugged where the building drain exits the house, and all the fixtures are capped, and you filled it with water to the roof vent (a standard leak test for rough DWV plumbing), you want everything to empty when you unplug the building drain. So don't create dead ends that will hold water/sewage that are connected to live DWV.

Cheers, Wayne
it looks like one might be a candidate if I were to cut it not where I previously marked it in red, but at the slope (blue line - see picture), while the other image from before needs to be removed.

And just so I know moving forward, if this was wet vented, is it allowed to drop down like that if the pipe it’s draining into to be wet vented is at a much lower elevation? Or, like the maximum distance a 2” line can travel is 5’ before wet vent, is there also an elevation parameter to consider? In other words should the wyes/combos be rolled “Flat” in a wet vented system
 

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wwhitney

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it looks like one might be a candidate if I were to cut it not where I marked it but at the slope (blue line), while the other needs to be removed.
Your pictures only show the downstream end of the improper horizontal dry vent. If the upper end of that vent is connected to a vent stack to the roof, then it could fill up with water if you cap it. So you need to disconnect it at the upper end. If you then cap it at the upper end and even left it in place with the downstream connection, it could drain out. If the correct fittings were used (I didn't check), it could even be used as a drain in the future. [Or you could disconnect at both ends, and abandon the pipe.]

And just so I know moving forward, if this was wet vented, is it allowed to drop down like that if the pipe it’s draining into to be wet vented is at a much lower elevation? Or, like the maximum distance a 2” line can travel before wet vent, is there also an elevation parameter to consider? In other words should the wyes/combos be rolled “Flat” in a wet vented system
Trap arms (from trap to vent connection, wet or dry) are regulated in length and elevation. Horizontal wet vents are generally considered to need to stay horizontal (although I think that's open to interpretation), but that horizontal includes any slope up to 45 degrees off horizontal. So I see no issue with, for example: tub trap -- compliant tub trap arm -- compliant dry vent takeoff -- steeply sloping (but still horizontal) wet vent -- compliant shower trap arm connection for wet venting the shower.

Cheers, Wayne
 

Kevinjm4

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The lav absolutely requires a dry vent in the right hand wall. A variant on option (2) would be simplest: make the lav a 2" drain and vent, use it to wet vent the WC, put a dry vent on the tub that rises into the left hand wall without going horizontal below the floor, and use it to wet vent the shower.

But if you absolutely want to avoid vents in both walls, you can do something like the diagram below. Red is 3", Blue is 2", Green is 1-1/2". [Edit: none of the drains are 1-1/2", that was an error and I updated the diagram. The lav dry vent can be 1-1/2".] The idea here is that the lavatory can wet vent the tub and the shower by crossing over the beam through a joist bay. If the shower and tub drains are below the joists, it's probably best for the lav drain to cross over the beam fairly low and then just gradually drop below the joists to join the tub drain.

The lav then wet vents the tub; with a 2" trap on the tub, the tub trap arm can be up to 60" in length, so that the maximum allowable run from the tub trap to the wye where it joins the lav (along with a 2" maximum drop). The combined drain goes on to join the shower and wet vent it, too.

That doesn't address the WC, so you route it under the joists near to the right hand wall to pull a 2" dry vent off it (with a combo, which could be rolled up to 45 degrees off vertical) that can rise up into the wall, within 6' of the closet flange, measured along the pipe. Within the wall the 2" WC dry vent and the 1-1/2" lav dry vent can join at a height at least 6" above the lav flood rim; if the distances work out, the two dry vents could be in the same stud bay, so you don't have to drill any studs (otherwise it would be easier to bring the 1-1/2" vent to the 2" vent, rather than vice versa).

I'm not sure exactly what's going on at the bottom of the page with the footer and the existing 3" drain, but you just connect your new 2" drain and new 3" WC drain to the existing 3" line however is required (everything is vented), either separately or by combining them first if that's easier.

Cheers, Wayne

View attachment 80738
The lav absolutely requires a dry vent in the right hand wall. A variant on option (2) would be simplest: make the lav a 2" drain and vent, use it to wet vent the WC, put a dry vent on the tub that rises into the left hand wall without going horizontal below the floor, and use it to wet vent the shower.

But if you absolutely want to avoid vents in both walls, you can do something like the diagram below. Red is 3", Blue is 2", Green is 1-1/2". [Edit: none of the drains are 1-1/2", that was an error and I updated the diagram. The lav dry vent can be 1-1/2".] The idea here is that the lavatory can wet vent the tub and the shower by crossing over the beam through a joist bay. If the shower and tub drains are below the joists, it's probably best for the lav drain to cross over the beam fairly low and then just gradually drop below the joists to join the tub drain.

The lav then wet vents the tub; with a 2" trap on the tub, the tub trap arm can be up to 60" in length, so that the maximum allowable run from the tub trap to the wye where it joins the lav (along with a 2" maximum drop). The combined drain goes on to join the shower and wet vent it, too.

That doesn't address the WC, so you route it under the joists near to the right hand wall to pull a 2" dry vent off it (with a combo, which could be rolled up to 45 degrees off vertical) that can rise up into the wall, within 6' of the closet flange, measured along the pipe. Within the wall the 2" WC dry vent and the 1-1/2" lav dry vent can join at a height at least 6" above the lav flood rim; if the distances work out, the two dry vents could be in the same stud bay, so you don't have to drill any studs (otherwise it would be easier to bring the 1-1/2" vent to the 2" vent, rather than vice versa).

I'm not sure exactly what's going on at the bottom of the page with the footer and the existing 3" drain, but you just connect your new 2" drain and new 3" WC drain to the existing 3" line however is required (everything is vented), either separately or by combining them first if that's easier.

Cheers, Wayne

View attachment 80738

I think I’m going to try and have a. Dry vent up each wall. Maybe you could help me with that I’m having a hard time seeing how all that comes together. I posted here (forgot we had this conversation going already):

 

wwhitney

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I think you'd be better off copying that new post over into this thread and deleting or blanking the other thread. Keeps all the info in one place. But if not, at least add a link to this thread.

Your question there is fairly open ended, so I'll reply hopefully later today. Edit: Oh, and the diagram there doesn't show what other walls might be available for running vents. And is the tub so far from the wall you want the vent in? On an alcove tub the tub waste and over flow is typically right next to a wall.

Edit: Lastly, I'm curious why you decided to dry vent the tub rather than wet vent it via the lav drain as in the diagram I drew?

Cheers, Wayne
 

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I think you'd be better off copying that new post over into this thread and deleting or blanking the other thread. Keeps all the info in one place. But if not, at least add a link to this thread.

Your question there is fairly open ended, so I'll reply hopefully later today. Edit: Oh, and the diagram there doesn't show what other walls might be available for running vents. And is the tub so far from the wall you want the vent in? On an alcove tub the tub waste and over flow is typically right next to a wall.

Edit: Lastly, I'm curious why you decided to dry vent the tub rather than wet vent it via the lav drain as in the diagram I drew?

Cheers, Wayne
Thanks for the reply. I will copy the other and pot here then delete thank you.

As far as not doing it the other way, I’m not opposed and may do it the way you drew up, but I was looking at my other wall where the tub and shower are and most likely I could route the vent up that, not go through the roof there, run it through the attic, and tie into another vent 15’ away that’s already going through the roof. Also you mentioned this as a simpler option compared to the one you drew up. Basically I want to have both options solidly laid out so I’m ready for either.

Yes the post was basic and open ended was looking for principals but application to my situation is always helpful.

The tub is a freestanding clawfoot tub so the drain will be a bit further from wall than a normal alcove would be but not much further away.

The walls that are able to be vented are the left and the right. Top and bottom (north and south) cannot be used to venting.
 

Kevinjm4

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The lav absolutely requires a dry vent in the right hand wall. A variant on option (2) would be simplest: make the lav a 2" drain and vent, use it to wet vent the WC, put a dry vent on the tub that rises into the left hand wall without going horizontal below the floor, and use it to wet vent the shower.

But if you absolutely want to avoid vents in both walls, you can do something like the diagram below. Red is 3", Blue is 2", Green is 1-1/2". [Edit: none of the drains are 1-1/2", that was an error and I updated the diagram. The lav dry vent can be 1-1/2".] The idea here is that the lavatory can wet vent the tub and the shower by crossing over the beam through a joist bay. If the shower and tub drains are below the joists, it's probably best for the lav drain to cross over the beam fairly low and then just gradually drop below the joists to join the tub drain.

The lav then wet vents the tub; with a 2" trap on the tub, the tub trap arm can be up to 60" in length, so that the maximum allowable run from the tub trap to the wye where it joins the lav (along with a 2" maximum drop). The combined drain goes on to join the shower and wet vent it, too.

That doesn't address the WC, so you route it under the joists near to the right hand wall to pull a 2" dry vent off it (with a combo, which could be rolled up to 45 degrees off vertical) that can rise up into the wall, within 6' of the closet flange, measured along the pipe. Within the wall the 2" WC dry vent and the 1-1/2" lav dry vent can join at a height at least 6" above the lav flood rim; if the distances work out, the two dry vents could be in the same stud bay, so you don't have to drill any studs (otherwise it would be easier to bring the 1-1/2" vent to the 2" vent, rather than vice versa).

I'm not sure exactly what's going on at the bottom of the page with the footer and the existing 3" drain, but you just connect your new 2" drain and new 3" WC drain to the existing 3" line however is required (everything is vented), either separately or by combining them first if that's easier.

Cheers, Wayne

View attachment 80738
Wayne, I’ll post here instead of copying and pasting the other, and I’ll delete the other.

And I’ll just ask this more straightforwardly and specific. With my situation if I desire to dry vent the left and right walls, I need help with how to do this on the left wall fixtures (and maybe the right too, see diagram), given that I do not have much room (elevation) in the crawl space and the fixtures’ drains are not in the wall like a lav is. I’m having trouble comprehending how a drain/vent is routed fittings used and how) for something like a tub where the drain is 12-18” away from the wall, and it’s drain also runs away from said wall. I can’t say for sure yet where my tub drain will be in the floor but at most 18” from the wall but probably closer to 12-15” away.

I am also unsure about required size of pipe for the vents in this layout, the left and right walls (WC/lav and tub/shower). 1.5” vent for the left wall would be ideal for framing purposes but 2” may be achieved if needed.

I’m assuming for the drains it’s toilet 3, lav 1.5, tub 2, shower 2.

I will draw another diagram with my attempt to route the dwv.
 

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Reach4

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And I’ll just ask this more straightforwardly and specific. With my situation if I desire to dry vent the left and right walls, I need help with how to do this on the left wall fixtures
 

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wwhitney

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What Reach4 drew, with the elaboration:

(a) you'll need a short section parallel to the wall generally, to use a wye or combo for a vent takeoff, unless you are OK with the altitude loss caused by a brief vertical segment that using a san-tee and LT90 to cause and

(b) you don't have to bring the drain all the way to underneath the wall, as the vent can be at up to 45 degrees off plumb. So that means the vent can move towards the footprint of the wall as it rises up towards the floor, and just has to reach the wall before emerging through the floor. If taking the vent off the horizontal with a wye or combo, you can roll that wye or combo up to 45 degrees.

Oh, and yes, a 1.5" dry vent is sufficient for a tub and a shower. The tub trap and trap arm could be 1.5" (although I like 2"), but the wet vent, from the tub vent takeoff to where the shower drain joins, must be 2".

Cheers, Wayne
 

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What Reach4 drew, with the elaboration:

(a) you'll need a short section parallel to the wall generally, to use a wye or combo for a vent takeoff, unless you are OK with the altitude loss caused by a brief vertical segment that using a san-tee and LT90 to cause and

(b) you don't have to bring the drain all the way to underneath the wall, as the vent can be at up to 45 degrees off plumb. So that means the vent can move towards the footprint of the wall as it rises up towards the floor, and just has to reach the wall before emerging through the floor. If taking the vent off the horizontal with a wye or combo, you can roll that wye or combo up to 45 degrees.

Oh, and yes, a 1.5" dry vent is sufficient for a tub and a shower. The tub trap and trap arm could be 1.5" (although I like 2"), but the wet vent, from the tub vent takeoff to where the shower drain joins, must be 2".

Cheers, Wayne
If I’m venting up both walls, here’s what I’ve gathered correct me where I’m wrong. Thanks!
What Reach4 drew, with the elaboration:

(a) you'll need a short section parallel to the wall generally, to use a wye or combo for a vent takeoff, unless you are OK with the altitude loss caused by a brief vertical segment that using a san-tee and LT90 to cause and

(b) you don't have to bring the drain all the way to underneath the wall, as the vent can be at up to 45 degrees off plumb. So that means the vent can move towards the footprint of the wall as it rises up towards the floor, and just has to reach the wall before emerging through the floor. If taking the vent off the horizontal with a wye or combo, you can roll that wye or combo up to 45 degrees.

Oh, and yes, a 1.5" dry vent is sufficient for a tub and a shower. The tub trap and trap arm could be 1.5" (although I like 2"), but the wet vent, from the tub vent takeoff to where the shower drain joins, must be 2".

Cheers, Wayne
heres my attempt based on what I’ve gathered. Check my work? Thanks!
 

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Reach4

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Nope. You have horizontal dry vent to the tub.
 

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First I will try and slope it up 45, but if I don’t have the room/elevation I’ll have to route it as you drew it up
Perhaps you misunderstood the sketch. My new lines were in the horizontal plane (with the slight slope, of course).

I did not describe the trap. The trap will give some adjustability. But the point is that the trap arm went to the wall. The path got vented at the wall. Then the vented waste turned and went where it needed to get to.
 
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