Moving Kitchen Sink and Adding Bathroom

[Still_Learning]

Long-time reader now hoping to get some feedback on whether this layout is possible (sorry for the erasure marks). Basically, the kitchen sink was next to the stack but now I want to move it in front of a window about 8-10' away. Based on my reading, I think a loop vent is best for this since there's nowhere to put a new vent between the existing windows and door (top-left quadrant of picture). This is a single-story with a basement so no other fixtures above these.

I also want to add a bathroom near the stack with back-to-back toilets and sinks. Based on what I've learned from this site, it seems like this is doable if I use a Double Combination Wye for the toilets and a double fixture for the sinks.

Assume a cleanout is added to the loop vent drain; forgot to draw that

Now my questions:
1) Regarding Label D on the diagram, is there a maximum length that vent can be before running to the roof (ex. I feel like I've read 5 feet).

2) For Label E, should I tie that tub drain into the vent as pictured or will relying on the main stack vent be okay? Distance should be about 6 feet from that tub to main stack.

3) Am I even close or is this a recipe for disaster?

 

[wwhitney]

I don't believe you can use a loop vent unless the sink is on an island. Are you under the IPC or UPC? For the IPC you could use an AAV. Under the UPC your options are more limited.

Also, your tub dry vent E needs to be a vertical takeoff (at most 45 degrees off plumb) and stay vertical until at least 6" above the tub flood rim.

Lastly, the kitchen drain can't participate in any bathroom wet venting. So it needs to stay separate from the bathroom fixtures until after they are all vented. E.g. the dry vented tub could wet vent the other tub, then the combined drain could join the kitchen drain, and that combined drain could join the stack below both the WCs (i.e. move B below C).

Cheers, Wayne

 

[Sponsor]

 

[Still_Learning]

Thanks @wwhitney. I think that makes sense. I'm under UPC so AAVs are a no-go. I read on another post here where a poster said they use this setup for windows where there is a beam on both side and no way to run a vent. I've added a new diagram to the original post with the tub vent in a new location. I'm wondering if I'm on the right track.

Thanks for your help!

 

[wwhitney]

I don't believe the idea that a loop vent can be used for other than an island sink. The UPC section that allows it is 909, which is titled "Special Venting for Island Fixtures."

What you can do is run the vent up the wall as high as possible below the window. Hopefully you have room for a vent pipe between the window and door, or else on the other side of the window. If the vent can rise under the window sill to a height of at least 6" above the counter before turning horizontal, that complies with the normal rules. If not, there is an allowance in 905.3 when rising that high is "prohibited by structural conditions" to turn horizontal lower. But you have to plumb the vent as if it it were drain (drainage fittings and patterns), from the height of 6" above the counter and below.

The other possibility, depending on the horizontal distance, is to put your san-tee to one side of your window. Then a 1-1/2" trap arm is allowed to be up to 42". So if the pipe run from your trap u-bend to that san-tee can be 42" or under, that would work. If the window is too wide for that, scratch that option.

As to your tub vent, the tub on the right has to join the first tub after the yellow dry vent, not before. And then the kitchen drain can join after that. If you use 1-1/2" tub traps, both trap arms are limited to 42" (on the left tub, from the trap to the yellow dry vent; on the right tub, from the trap to the horizontal combo where it joins the left tub). If you need longer than that, you can use a 2" trap on a tub to increase the trap arm allowance to 60". [You could do the same on the kitchen sink, I guess, but that would be more unusual.]

Cheers, Wayne

 

[John Gayewski]

How wide is the window? Come up beside the window and start your trap arm there.

 

[Still_Learning]

Thanks @wwhitney and @John Gayewski. Sorry for the Thanksgiving delay. I've added a new diagram (plumbing3). Do I have this correct or does the vent/drain to the left of the window need to be in one vertical line?

Will the drain marked D need an additional vent to the right of the door if the run is 10-12 feet?

 

[wwhitney]

So what is the width of the window (plus framing, so outside of king stud to outside of king stud), and where along that width will the drain center line land?

1) This depends on the elevation of the yellow horizontal line (vent). If it's 6" or more above the countertop, it's fine.

If it can't be that high (because the window is lower), and you are under the UPC, and the horizontal distance between the sink drain and the vertical yellow vent to the left of the window is under 42", then you should move the sink san-tee to the left to be under the vertical yellow vent to the left of the window (or almost under, with a segment rising at a 45 under the window to make it past the window). If you are under the IPC, you have up to 72" for a 1-1/2" trap arm with perfect 1/4" per foot pitch.

2) No, the vent just protects the trap; drain length after that doesn't matter.

Cheers, Wayne

 

[Still_Learning]

The window is 82" so sounds like I either need to size up to 2" for the trap arm to be able to do 60" horizontal distance or move the sink to the left window. Right?

Good to know about the drain length. Two other things I want to confirm:

1) If both tub drains are within 5 ft. of the main stack, would I need the vent E for the tubs?

2) The vent to the roof for the kitchen sink can be 1.5" right?

 

[wwhitney]

1) For a 60" trap arm you'd need a 2" tub trap. Then if you run each trap arm separately to the stack, and if the only fixtures draining into the stack above the tubs are the two lavs, then the tubs would be vertically wet vented. To tie into the stack, you either need to stack 3x3x2 san-tees for the two tubs, or use an approach geometry that allows you to use a single 3x3x2x2 san-tee with sanitary side inlet (where the side inlet has the same curvature as the main inlet), or a 3x3x2x2 double fixture fitting. And it's worth reiterating that the 2" trap arm can only fall 2" between the trap outlet and the vent connection (in this case the stack).

2) A vent serving only a kitchen sink can be 1.5", and it can go up through the roof, or recombine with your stack in the attic or ceiling joists above.

Cheers, Wayne

 

[Still_Learning]

Many thanks @wwhitney! I now feel like this project might be doable. Regarding the 3x3x2x2 san-tee with side inlet:

1. Would the kitchen sink tie into the side inlet?
   
   
2. If I used a double fixture fitting and tied in the kitchen sink below it, would the drain line for the kitchen sink have a maximum fall of 2" or is it good to go because of the separate vent?

 

[wwhitney]

1) In my previous post, I was discussing only the tub drains. If you want to use the stack to vent the lavs, the tubs, and the WCs, the order from top to bottom on the stack would have to be lavs - tubs - WCs - kitchen sink.

2) The fall limit of one pipe diameter applies between the trap outlet and the vent connection. After the vent, the drain can fall without restriction.

Cheers, Wayne

 

[Still_Learning]

Thanks, very helpful. I've liked all the posts. Please let me know if there's another way to show my appreciation. This forum is great!

 

[Still_Learning]

Okay, bumping this for one more (hopefully easy) question. If I proceed with the plumbing3 diagram in the first post, does it matter if the drain line that combines the tubs and kitchen sink meets the stack above the toilets vs. below the toilets?

The diagram has it joining below the toilets but there'd be more headroom in the utility area if they could join above the toilets. Thanks in advance!

 

[wwhitney]

Good question. I was going to say that the WCs had to be above the kitchen sink (so only bathroom fixtures above the WCs), but that's not true for the UPC. The UPC allows vertical wet venting within a story, for any number of 1 or 2 DFU fixtures draining into the stack, and serving to vent up to 4 fixtures. Since the lavs (1 DFU each) are dry vented by the top of the stack, and the tubs and kitchen sink (2 DFU each) are separately vented, the wet vent is only a vent for the two WCs.

Sizing wise, the wet vent has to be one size bigger than the requisite vent size (2" for a WC), and one size bigger than the minimum drain size for the drainage carried (8 DFUs if the lavs, tubs, and kitchen sink come in above, which also means 2"). So as long as the stack is 3" above the WC connection, you can have the WCs below the lavs, tubs, and kitchen sink.

https://up.codes/viewer/california/ca-plumbing-code-2019/chapter/9/vents#908.1

I may have mentioned this above already, but the distance from the closet flange to the stack, measured along the drain pipe, is limited to 6'.

Cheers, Wayne

 

[Still_Learning]

Alright, I'm about halfway into this project now and things are going alright but I'm not going to keep saying this is my last question (ha!) because who really knows what I'll run into. Two new questions with diagrams!

1) When tying a horizontal drain into the main stack, do I have to use a sanitary tee or can I drop it vertically into a wye lower in the stack like in the first image?

2) When using a double 45 wye for back-to-back toilets, do I need the street 45s off the wye (Diagram A in picture 2) as I've typically seen or can I drop the toilets directly into the wye as in Diagram B?

Again many many thanks for getting me this far!

 

[Reach4]

1) When tying a horizontal drain into the main stack, do I have to use a sanitary tee or can I drop it vertically into a wye lower in the stack like in the first image?

You can use the wye if the drainage has already been vented.

2) When using a double 45 wye for back-to-back toilets, do I need the street 45s off the wye (Diagram A in picture 2) as I've typically seen or can I drop the toilets directly into the wye as in Diagram B?

If you can run a toilet line into the wye, it is fine to not have a 45. HOWEVER either way, the toilet will be required to be be vented. That venting could be via the middle line from above. I think that line could be a dry vent from the roof, or could be a wet vent because the vented lavatory or vented shower or vented tub is coming in from above. But having a 45 in there is optional and is not going to add performance or compliance.

There are some good 45 degree output closet flanges, but it seems to me that would be trickier to get glued into place.

 

[John Gayewski]

Any of those diagrams are ok. A toilet can't be vented above the trap so your good. The horizontal drain is a fine way to drain as long as your trap is vented from above.

 

[Still_Learning]

Awesome! Thank you both and hope you are having a great Christmas!