Venting side by side bathrooms, and another bathroom a floor below

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Tudorrenovator

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Yes, under the IPC a 1.5" dry vent can vent a whole bathroom group.

Wayne
Wayne, I updated my drawing, could you take a look?

Is the lav 1.5” cent enough to vent the bathroom 2 group at the the top left? Is the position after the wc on the horizontal drain ok?



I believe the 1/2 bath layout is now properly vented?



For bath group 1 in the top right, the lav and the tub meet at a 2” wye, with the lave dry vented to the room stack. But with the space constraints in the spot, it connects below the wc. My question is, is the 3” main vent stack next to the wc enough to vent the wc? The wc sits directly above a 3” sanitee and ties in without a bend- just right on top. Does that work? Any thoughts on how to fix if it doesn’t? I added photos below
 

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Tudorrenovator

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Wayne, I updated my drawing, could you take a look?

Is the lav 1.5” cent enough to vent the bathroom 2 group at the the top left? Is the position after the wc on the horizontal drain ok?



I believe the 1/2 bath layout is now properly vented?



For bath group 1 in the top right, the lav and the tub meet at a 2” wye, with the lave dry vented to the room stack. But with the space constraints in the spot, it connects below the wc. My question is, is the 3” main vent stack next to the wc enough to vent the wc? The wc sits directly above a 3” sanitee and ties in without a bend- just right on top. Does that work? Any thoughts on how to fix if it doesn’t? I added photos below
 

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John Gayewski

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I thought I read in the ipc a vent needed to be downstream of fixtures. I'm upc guy and go with the theory "air don't care" meaning a vent can be anywhere within the trap arm length max. But in ipc air does care and the lav must be last and within the trap arm length (which are longer in ipc) if it's venting the bathroom group. I'll let wanye correct me if I'm wrong.
 

Tudorrenovator

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I thought I read in the ipc a vent needed to be downstream of fixtures. I'm upc guy and go with the theory "air don't care" meaning a vent can be anywhere within the trap arm length max. But in ipc air does care and the lav must be last and within the trap arm length (which are longer in ipc) if it's venting the bathroom group. I'll let wanye correct me if I'm wrong.
Here the lavs would be venting right off the sanitee after the trap, dry venting to the roof. Is that sufficient?
 

wwhitney

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Nice isometric diagram! The DWV looks OK. My comments:

- Upstairs, you show a 3" vent coming off the horizontal branch and rising through the roof. That vent is superfluous and can be omitted. I may be misinterpreting the isometric, but if the vent is coming off the top, the way you've drawn it isn't quite right--you'd need a downstream facing wye or combo, then another 45 after it goes vertical to get it to rise at an angle.

- The lav in Bath 2 is wet venting the Bath 2 tub and both WCs, which the IPC allows.

- You need to be sure the tub trap arm comply with the trap weir rule, which I've mentioned before but perhaps not by name. Namely from the trap outlet to the wye/combo where the lav joins the tub, the fall is limited to one pipe diameter.

Cheers, Wayne
 

wwhitney

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But in ipc air does care and the lav must be last and within the trap arm length (which are longer in ipc) if it's venting the bathroom group.
I'm not exactly sure what you mean. If by "last" you mean "most upstream" then in the drawing for Bath 2 it's not actually distinguishable DWV network-wise which is more upstream, the lav or the WC. You can say the WC is more upstream because it has the larger pipe going to it, or because it's physically farther from the drain stack.

But just looking at the graph (the collection of joints and pipes connecting those joints), all you can say is that the lav/WC joint is the upstream most joint. And that's all the wet venting rules require.

Cheers, Wayne
 

John Gayewski

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I'm not exactly sure what you mean. If by "last" you mean "most upstream" then in the drawing for Bath 2 it's not actually distinguishable DWV network-wise which is more upstream, the lav or the WC. You can say the WC is more upstream because it has the larger pipe going to it, or because it's physically farther from the drain stack.

But just looking at the graph (the collection of joints and pipes connecting those joints), all you can say is that the lav/WC joint is the upstream most joint. And that's all the wet venting rules require.

Cheers, Wayne
912.1.1 ipc I guess it's where the drawing didn't square. Wouldn't the shower need to come in upstream of the toilet on bath #3? Could be I'm drunk.
 

wwhitney

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912.1.1 ipc I guess it's where the drawing didn't square. Wouldn't the shower need to come in upstream of the toilet on bath #3?
912.1.1 on vertical wet venting does say that the WC has to be at the bottom of the vertical wet vent. But how does that apply to the diagram? I don't see any vertical wet vents, and there is no bath #3.


I do agree that the wet venting of Bath #1 WC is a bit unusual, as is the wet venting of the 1/2 Bath WC. In each case the WC fixture drain is vertical, the wet vent comes in horizontally, and the combined drain exits vertically. I.e. it is or could be a san-tee connection. But the wet vent ends at that connection in both cases, so the wet vent is all horizontal. Which I would think means the horizontal wet venting rules apply.

Cheers, Wayne
 

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912.1.1 on vertical wet venting does say that the WC has to be at the bottom of the vertical wet vent. But how does that apply to the diagram? I don't see any vertical wet vents, and there is no bath #3.


I do agree that the wet venting of Bath #1 WC is a bit unusual, as is the wet venting of the 1/2 Bath WC. In each case the WC fixture drain is vertical, the wet vent comes in horizontally, and the combined drain exits vertically. I.e. it is or could be a san-tee connection. But the wet vent ends at that connection in both cases, so the wet vent is all horizontal. Which I would think means the horizontal wet venting rules apply.

Cheers, Wayne
Bath 3 was labeled on the previous drawings, he's now calling it bath 2 second floor.

Maybe it's the way it's worded that makes this oblique to me. They define a vertical wet vent but don't distinguish that it must be vertical (maybe becuse it is in the name), they only say it's defined or shall be the "the vent" between the dry vent connection and the lowest fixture drain connection. This is where maybe the language probably invented to be obvious. But really they don't say a vertical at vent is a vertical pipe. The lowest fixture drain connection on the second floor 2nd bathroom is the shower drain connection.
 

wwhitney

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Chapter 2 of the IPC is missing definitions for "dry vent" and "wet vent" which I agree is a deficiency. In contrast the UPC has the definitions:

"Dry Vent. A vent that does not receive the discharge of any sewage or waste."
"Wet Vent. A vent that also serves as a drain."

If we can assume that the IPC means the same thing with those terms, then it seems clear to me that, absent some other Chapter 2 definition, a "vertical wet vent" is a wet vent that is vertical. At least "vertical" is defined in Chapter 2.

Of course, that doesn't work so well for "horizontal wet vent" as it may contain sections that are vertical. There's a bit of a saving grace in the definition of "Horizontal Branch Drain" which starts out "A drainage branch pipe extending laterally from a soil or waste stack or building drain, with or without vertical sections or branches, . . ." So we can define "horizontal wet vent" as a "horizontal branch drain which is a wet vent."

But all of this would definitely be clearer if it were spelled out. Right now we just have to apply our notions of common sense.

Cheers, Wayne
 

John Gayewski

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Could be a different section that S pointed out to me at
Chapter 2 of the IPC is missing definitions for "dry vent" and "wet vent" which I agree is a deficiency. In contrast the UPC has the definitions:

"Dry Vent. A vent that does not receive the discharge of any sewage or waste."
"Wet Vent. A vent that also serves as a drain."

If we can assume that the IPC means the same thing with those terms, then it seems clear to me that, absent some other Chapter 2 definition, a "vertical wet vent" is a wet vent that is vertical. At least "vertical" is defined in Chapter 2.

Of course, that doesn't work so well for "horizontal wet vent" as it may contain sections that are vertical. There's a bit of a saving grace in the definition of "Horizontal Branch Drain" which starts out "A drainage branch pipe extending laterally from a soil or waste stack or building drain, with or without vertical sections or branches, . . ." So we can define "horizontal wet vent" as a "horizontal branch drain which is a wet vent."

But all of this would definitely be clearer if it were spelled out. Right now we just have to apply our notions of common sense.

Cheers, Wayne
I guess none of that matters because the notion of air needing to be coming from a certain direction must be a memory from a different section or just plain misunderstood with a different context in mind. I saw circut venting in ipc needed to be between the two upper most fixtures, but that still doesn't seem to me it would be what I had previously interpreted as air being directional under ipc. My memory was venting and direction of flow were intended to be "parallel". I guess the circut venting kind of says that...
 

Tudorrenovator

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Nice isometric diagram! The DWV looks OK. My comments:

- Upstairs, you show a 3" vent coming off the horizontal branch and rising through the roof. That vent is superfluous and can be omitted. I may be misinterpreting the isometric, but if the vent is coming off the top, the way you've drawn it isn't quite right--you'd need a downstream facing wye or combo, then another 45 after it goes vertical to get it to rise at an angle.

- The lav in Bath 2 is wet venting the Bath 2 tub and both WCs, which the IPC allows.

- You need to be sure the tub trap arm comply with the trap weir rule, which I've mentioned before but perhaps not by name. Namely from the trap outlet to the wye/combo where the lav joins the tub, the fall is limited to one pipe diameter.

Cheers, Wayne
Thank you, really appreciate it. You are
Correct on the wye I need to update the the chart. I’m taking this all in and will provide an update soon.
 
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