2 story DWV Rough Layout

[Gundraw]

Looking at a workshop with a simple first floor 1/2 bath but want to make sure I could add a potential full bath to the second story. (The second bath would be directly above the first bath) Trying to keep the number slab (and roof) penetrations to a minimum.

Does this rough layout meet code for venting? Is there a better way to use less penetrations through the slab?

 

[wwhitney]

Try the layout below, it complies with UPC and IPC, not sure what is in use in your area. The changes:

- You can run some 4" if you want, but 3" is adequate for everything shown, and is just required for the drains carrying a WC. [Except that the UPC requires 3" on the vertical wet vent between the upstairs shower and the upstairs WC, as you drew. For the IPC that short segment could be 2".]

- For the lav to wet vent the downstairs WC, you need to have its drain join the WC drain before either one joins anything else. I drew that as a vertical separation between the drain from upstairs and the downstairs WC fixture drain, but it could be a horizontal separation instead.

- Lastly, you are showing two sinks downstairs, but I'm assuming only one is a lav, and that the other is a utility/slop/laundry sink. In which case its drain also needs to be kept separate from the WC and lav drains for the lav to wet vent the WC. [Actually under the UPC it wouldn't need to be kept separate if you used a 3" vertical wet vent between the lower sink on the stack and the WC fixture drain.]

Cheers, Wayne

 

[Sponsor]

 

[Gundraw]

Thank you Wayne!

I had to read your tips a couple times, but I think I understand.

Couple questions:

Perhaps I should clarify the sinks. The first floor sink by the WC will be a mudroom sink. So i am hoping to make it more of a utility sink than a classic bathroom sink. The second sink on the other side of the wall would be a kitchen sink. The upstairs sink would be a traditional lavatory. I was not aware the sink sizes/uses made a difference in plumbing, so I am elaborating in case this requires additional changes.


I think i get where the WC has to join the LAV wet vent before joining the drain. There are some reasons that I would really like to keep penetrations through the slab to a minimum. It seems vertical, or horizontal, I will have to have 4 protrusions through the slab, right? Left to right : Upstairs drain stack, closet flange for WC, Drain for LAV, Drain for utility sink.

Thanks for the help!

Try the layout below, it complies with UPC and IPC, not sure what is in use in your area. The changes:

- You can run some 4" if you want, but 3" is adequate for everything shown, and is just required for the drains carrying a WC. [Except that the UPC requires 3" on the vertical wet vent between the upstairs shower and the upstairs WC, as you drew. For the IPC that short segment could be 2".]

- For the lav to wet vent the downstairs WC, you need to have its drain join the WC drain before either one joins anything else. I drew that as a vertical separation between the drain from upstairs and the downstairs WC fixture drain, but it could be a horizontal separation instead.

- Lastly, you are showing two sinks downstairs, but I'm assuming only one is a lav, and that the other is a utility/slop/laundry sink. In which case its drain also needs to be kept separate from the WC and lav drains for the lav to wet vent the WC. [Actually under the UPC it wouldn't need to be kept separate if you used a 3" vertical wet vent between the lower sink on the stack and the WC fixture drain.]

Cheers, Wayne

 

[Terry]

 

[wwhitney]

Perhaps I should clarify the sinks. The first floor sink by the WC will be a mudroom sink. So i am hoping to make it more of a utility sink than a classic bathroom sink. The second sink on the other side of the wall would be a kitchen sink. The upstairs sink would be a traditional lavatory. I was not aware the sink sizes/uses made a difference in plumbing, so I am elaborating in case this requires additional changes.

Yes, the plumbing code distinguishes between lavatories and other sinks. Lavatory is not actually defined in the IPC, but I assume it means a sink for handwashing, vs kitchen/utility sink.

So the code compliant arrangement will vary depending on whether you call the sink by the WC a lavatory or a utility sink. Might be simplest to call it a lavatory even if you install a larger sink. If you call it a 2nd utility sink, you will need a separate slab penetration for a WC dry vent.

I think i get where the WC has to join the LAV wet vent before joining the drain. There are some reasons that I would really like to keep penetrations through the slab to a minimum. It seems vertical, or horizontal, I will have to have 4 protrusions through the slab, right? Left to right : Upstairs drain stack, closet flange for WC, Drain for LAV, Drain for utility sink.

If you want to minimize penetrations, you can get it down to 3 by combining the upstairs drain and the utility sink drain. Depends on whether running the upstairs drain horizontally over to near the downstairs fixtures is worth it or not.

And if you really want to minimize penetrations, you could either use a rear outlet WC or put in a raised platform for a bottom outlet WC to get all the drainage/vent connections above the slab. Then you'd only need one slab penetration for the building drain.

Cheers, Wayne

 

[Gundraw]

Terry,

I saw this diagram in some other discussions. I was hoping that without the tub, there would be a clever way of doing this to minimize stubs from the main drain.


Wayne,

Yes, I would like to avoid the "throne" toilet.

Let me be clear, there isn't a way of having both WC share a drain stack, then everything else have a separate drain/vent, like this with 2 penetrations:

Also, it should be noted, I am looking for useful SAFE plumbing, not necessarily what meets specific codes, if that makes sense.

 

[wwhitney]

So, the issue which controls the answer to your question is venting. If it were one story, it'd be no problem. But venting between stories is more complicated.

If you are under the IPC, then I think the stack on the right you propose for the sinks and the shower could be made to work under IPC 913 "Waste Stack Vent." That section doesn't allow WCs on the stack, but IPC 917 "Single Stack Vent System" may be possible for the stack on the left. But I'm not so familiar with those sections so I can't give you a definite answer.

One thing you definitely can do with normal wet venting allowances only is a configuration like the one below, that I alluded to earlier. I moved stuff left or right just to avoid crossing lines on the page.

Cheers, Wayne

 

[Terry]

There is no venting between floors.
A toilet that uses the vent for a downstairs toilet does not work.
Any wet venting is done on the SAME floor.
Vents from the lower floor may tie in at 42" above on the floor above. This is not new stuff here. Each floor is it's own entity.
You plumb it, vent it, and then have the vent take a ride upstairs and if they are nice, they let you tie in at 6" above that floors flood level.
Otherwise, the next post we see after you've disregarded our advice, is asking us how to fix the next set of problems.
Problems that should never have happened. I hope you're pulling a permit for this.

 

[Gundraw]

Thanks Wayne, does something like this fit the same bill with penetrations?

Terry, I am not inclined to disregard any of this advice. Just trying to find the most straight forward way of doing this (the right way).

Thanks!

 

[wwhitney]

On the last drawing, only if both the sinks on the lower level are lavatories. If one of them is a lavatory, then you could split the drains and send the non-lavatory over to connect to the other stack above the floor.

But it's the same number of floor penetrations as my last drawing. The only upside is that you have more flexibility on locating the drain penetration that will wet vent the downstairs WC, vs dry venting the downstairs WC.

How about a floor plan of the downstairs level?

Cheers, Wayne

 

[Gundraw]

On the last drawing, only if both the sinks on the lower level are lavatories. If one of them is a lavatory, then you could split the drains and send the non-lavatory over to connect to the other stack above the floor.

But it's the same number of floor penetrations as my last drawing. The only upside is that you have more flexibility on locating the drain penetration that will wet vent the downstairs WC, vs dry venting the downstairs WC.

How about a floor plan of the downstairs level?

Cheers, Wayne

So I could do something like this if both first floor sinks are utility sinks?

The bathroom is very simple, a toilet next to a big utility sink. It sits against a 6" wall so I can run all the DWV to the second floor in wall. On the other side is a kitchen sink (shown as a 3 section). My hope was to set the closet flange for the toilet, then as few penetrations as possible in the wall behind to service both of the 1st floor sinks, then someday, perhaps a full bath upstairs. Tips for where/how to do a cleanout?

 

[wwhitney]

Almost, see the diagram below.

Now that I think about it some more, the restriction of wet venting to bathroom group fixtures like a lavatory is only for horizontal wet venting. With just one sink and a WC, both the IPC (common venting) and the UPC (vertical wet venting) will allow you to use a kitchen or utility sink to wet vent the WC.

So on your floor plan, you can set your closet flange and set two 3" combos with vertical side branch below the slab for two 3" risers out of the slab. On the upstream combo, the WC connects to it horizontally under the slab, the riser gets a 3" cleanout fitting and then a 3" san-tee for one of the sinks (looks like the kitchen sink is closer). Above that san-tee the vent can reduce to 2" (UPC) or 1-1/2" (IPC).

Then to maintain the ability to use the downstream 3" riser for a drain for the future upstairs sink, you can't use it as a vent, just as a drain. So that sink's vent reconnects to the first sink's vent, at least 6" above both flood rims.

The details of how the upstairs bath DWV is likely to be plumbed aren't well expressed in the elevation (a vertical wet vent like that isn't so typical), but the basic idea shown is sound: how to connect things under the slab and on the first floor, and that you need both an upstairs drain and a downstairs vent crossing between the 1st and 2nd floors.

Cheers, Wayne

 

[Gundraw]

Wayne. Thank you! This is exactly what I was trying to figure out.

So now I have to ask (I'm not trying to be lazy, but want to be SURE about this under slab plumbing). Is there a way to get a closet flange at the proper 12" rough-in then sweep down (under slab), then another 90 so I can run the drain directly under where the 6"wall will later. This would allow the risers to be built into the wall Here is a vertical sketch.

I am assuming a 3" long sweep down/back from the closet flange then another 3" long sweep to the right will put the drain pipe too far back. Can I use a long sweep from the toilet then a 45? Didn't know if there was a standard way of doing this. I am also assuming a long sweep to change direction toward the sewer hookup.

Appreciate the help!

 

[wwhitney]

Under the WC you can use a closet bend or a quarter bend, but a LT90 is fine if you don't need mind that it will be deeper. Rotate the bend to have the outlet point at the wall at a 45 degree angle, instead of perpendicular to the wall. Then use a 45 under the wall, and an upright combo at each riser.

If that doesn't fit, there are other options.

Cheers, Wayne