Underslab plumbing mock-up

[Gundraw]

Here is a drawing with the theoretical future plans using all 4 stacks. I am assuming, based on your comments, that if I put in the piece in red, I can do the same thing with only 3 stacks?

 

[Jeff H Young]

Thats my thoughts no real benefit to 2 pipes side by side, however its all in the details of where the bathroom is going and the structural conditions.

 

[Sponsor]

 

[Reach4]

Most of MO uses IPC, but KC, MO uses UPC plumbing code.

 

[Jeff H Young]

Most of MO uses IPC, but KC, MO uses UPC plumbing code.

Thats good to know , Not sure how it might apply perhaps If IPC he could eliminate the stack for the lav and just wet vent the w/c with the kitchen and lav ?

 

[Gundraw]

Thats good to know , Not sure how it might apply perhaps If IPC he could eliminate the stack for the lav and just wet vent the w/c with the kitchen and lav ?

Jeff, I am fine putting a 4th riser in if this certainly satisfies UPC. I am putting in a 6" wall so do you see a potential structural issue with two risers in one stud cavity? If not, I will put them at 12" and move on.

 

[Jeff H Young]

looking good , if this is a house youll need more than a single 2 inch vent out the roof in upc. if its just one vent it will need be 3 inch

 

[Gundraw]

Thanks, Jeff. I really appreciate you and Wayne's help.

Just to be clear, is there some kind of code problem with having two risers come up in a single stud cavity? You have mentioned that a couple times and my original plan was to simply space the risers between studs.

 

[Jeff H Young]

no problem just wanting it to be simple you can have 2 pipes followig each other just a bit redundant

 

[Gundraw]

Lets just say that for some reason I find that I cannot drain the lavatory in that first riser. If that happens, riser 1 becomes a dry vent and useless for anything else. That leaves 1 stub for kitchen, 1 stub for lavatory.

If that becomes the case, and I dump a sink in a riser as well as two upstairs bathrooms like this:

I suppose I am asking as I would rather NOT put the double riser in the studs, but dont' want to short change future plumbing additions.

 

[wwhitney]

Two comments on your last diagram:

- You can not bring drainage down from the 2nd floor into a pipe that is venting the first floor.
- The lavatory could share the dry vent the kitchen sink is using, and its drainage could join the kitchen sink drainage before they jointly enter the slab.

I.e. 3 risers would be fine in that scenario: one for the WC dry vent (which the two sink dry vents ultimately connect to in/below the first floor ceiling), one for the kitchen/lavatory drainage, and one for the upstairs drainage. In fact two risers would suffice.

Two basic rules here:

- Dry vents don't get any drainage from above. [The lavatory draining into the WC's vent is an example of wet venting, and that is limited to fixtures on the same floor.]
- Once drains have been vented, you can combine them any way you like.

Cheers, Wayne

 

[wwhitney]

In fact two risers would suffice.

E.g. as below.

Cheers, Wayne

 

[Gundraw]

Wayne,
I really like that last layout. That clarifies things greatly. I also like that the vent line is easily defined so I can be sure to vent all fixtures consistently. The fact that I could dump both sinks into one drain (after merging them in the wall) actually makes using the second riser very simple and that leaves riser 3 available for whatever 2nd floor additions I want to add.

Thanks Wayne and Jeff, I believe I know how to proceed! When it comes to putting all of this in above the slab, I may check in to make sure my pipe sizes are correct for venting and fixtures.

 

[Jeff H Young]

Thats What Im talking about !

 

[Gundraw]

I glued up my risers and ran into a little bit of an issue: I put marks on the pipe and tried to line all of them up using the index notches cast into the side of the fittings. When I was done, I glued on the riser tubes (2') and found that I was actually a little bit off on all of them.

When I put the level on, nothing is off more than a 1/4"/ft. The "front" two are close to level, the next one back tilts one way about 1/8"/ft, the cleanout tilts the other way about 1/8"/ft. I was hoping to hide all of this inside a 6" wall. Is this off enough that I need to start over and try again?

Side view, not sure why the left-most elbow looks canted out... optical

Picture with a straight edge against all the pipes (and which way they lean):

Not sure how close all of this needs to be to perfect but I am concerned with fitting this in the wall.

 

[wwhitney]

1/4" is well within tolerances for this application. I bet you could close that gap with hand pressure.

You will need to stake things so they don't get pushed around by the concrete while the slab is poured--I have no experience with that, so can't advise on a good approach. But you could probably make the 1/4" go away when securing it for the pour, not that you need to.

Cheers, Wayne

 

[Gundraw]

1/4" is well within tolerances for this application. I bet you could close that gap with hand pressure.

You will need to stake things so they don't get pushed around by the concrete while the slab is poured--I have no experience with that, so can't advise on a good approach. But you could probably make the 1/4" go away when securing it for the pour, not that you need to.

Cheers, Wayne

I probably should have been specific, (I modified my post to reflect this information), they are off less than 1/4" per/ft. Roughly speaking, yes, in 2', one riser goes 1/4" 1 direction and the other pipe goes 1/4" in the other direction.

 

[Daniel Collick]

Jeff, perhaps my rationale for the two risers was simply so each bathroom could have its own branch down to the trunk, then I could plumb both bathrooms using the example that Terry used to post all the time.

I am guessing based on your comment that I could easily combine both upstairs bathrooms into one 3" branch?

There are many configurations where separate 3” vertical waste pipes would be beneficial, but as far as your layout is concerned you’re fine with one. If necessary, you could always turn one 3” into two 3” but on the vertical up towards the ceiling by using a wye and a street 45 rotated parallel with the top of the wye.

 

[Daniel Collick]

Points are well taken - I think i understand the basic holdup:

The vent for the downstairs WC either has to be a dry vent, or be wet vented via the first floor lavatory (not kitchen sink, etc). So if I could accomplish that. It really leaves the other two drops open for whatever I want (without the upstairs bathroom sharing the same riser as the downstairs kitchen sink).

Jeff, you are getting close, I have an upstairs area, but I am not really sure what is going to happen and when with respect to plumbing. I'm trying to keep a blank canvas in case we find a need. At a minimum, I would assume at some point down the road, the 2nd story will at least get a full bath, hence the original drawings. Also know that the way I am handling the area above these stubs, is I will have plenty of space to run drain pipes to other areas of the building.

I would be comfortable saying that at most, the second story would see 2 full bathrooms. It seems like an additional riser between studs, downstream of the first floor WC would allow me to simply copy and paste the same upstairs bathroom drain design a second time? Something like this perhaps:

View attachment 93174

From my research, it seems that all of this together is still suitable for a 3" main line. know that I will be switching to a 4" outside of the foundation.

Wet vents are awesome IMO. Nowadays many municipalities require us to wet vent as much as possible when below the flood-rim.

 

[Gundraw]

So in reviewing all of the information you have all shared, I think I can simplify this design now that I am putting in a dry vent for the WC. I believe something like this would meet code:

Thanks.

 

[Reach4]

Not sure. I think discharging the kitchen sink into the vent for the lavatory may not be acceptable vertical wet venting of the lavatory.