Plumbing layout. Need validation please

[Jim_B]

I've unsuccessfully been trying to hire a plumber (they'll all too busy) to add drain/vents for an upstairs bath room shower/sink addition (moving from 1/2 bath to full bath). Additionally, downstairs I'm moving a washer which is also results in a new drain/vent. I'm a pretty good DYI so think I can handle this with some education. (I have gotten a building permit - so that should help/hurt in the end...)

The upstairs bath has 2x8 joist that sit on a bearing wall.
I'm plumbing all the new fixtures with 2" PVC.
Given that I need to run a vent for the downstairs laundry and I want to cut holes over the bearing portion of the joists - I'm running the vent in the floor over to an existing 3" stack (ABS - will connect 42+" up with compression sleeve).
I'm planning on draining the new shower/sink down to the existing 2" laundry and at the same time extending this pipe up to the joist cavity and adding the new venting to it.

If I were to execute this correctly - does anyone see issue with my design? (hopefully these pics relay the thoughts). Thanks

 

[Reach4]

Trap arms (pipe between U-bend and the vent, need to be venting before going down (other than the 1/4 inch/ft slope.
This can be a wet vent or dry vent.

 

[Sponsor]

 

[Tuttles Revenge]

Your shower trap needs to be vented before the trap arm drops down. And the sink vent needs to continue upwards through the roof or at least 6" above its flood level before it travel horizontally through the wall to the existing vent.

 

[Jim_B]

Thank you for the responses - considering I need to keep a portion of the venting within the joists. Is this approach valid?

 

[wwhitney]

considering I need to keep a portion of the venting within the joists.

Stop right there. You can't run any dry vents for the second story fixtures in the second story floor joists.

You sink needs a vent. A dry vent running up alongside the doorway, and then either up through the roof separately, or combining with the 3" stack in the attic, would work well. Or, as you are in a state using the IPC, you could use an AAV under for the sink.

Your vented sink drain can wet vent the shower. That would be a drain configuration similar to the blue lines in your last picture.

Cheers, Wayne

 

[Reach4]

Your vented sink drain can wet vent the shower. That would be a drain configuration similar to the blue lines in your last picture.

Are you thinking maybe with a double santee with the top port plugged?

I was thinking a medium sweep from the vented lav into the top of a santee. Then the shower goes into the side of the santee.

 

[wwhitney]

Mostly I meant a geometry where the shower trap arm meets the lav drain (wet vent) before the trap arm has fallen more than 1 diameter. Having the combined drain simultaneously turn downward at that juncture is complicated, as you point out. So having them join earlier would be simpler; I'm not clear on the drain geometry in plan.

Cheers, Wayne

 

[Reach4]

So having them join earlier would be simpler; I'm not clear on the drain geometry in plan.

Yeah, that "view from above" is confusing.

And I don't see how that relates to the photo. And the marks on the photo -- don't understand those either. And what are the green marks? I would guess the lavatory will be above where the blue and green lines touch, on one side of the wall or the other.

A photo that shows the location of the lavatory and shower would be a good thing. And where there are existing drain lines, how about an arrow showing flow direction.

 

[Jim_B]

First of all - thank you all for helping it's greatly appreciated - sorry my mockups are confusing hopefully these pics help.

Given the feedback for the new sink, its drain line will feed to an existing 2" drain available in the wall in the floor below. An AAV will be installed under the sink for venting. (I live in North Carolina and it sounds like this is OK per IPC). I think this is the best/easiest solution (unless doing differently will help the shower situation as outlined below).

That leaves the shower drain/vent. I've given up on the idea of using the existing 3" stack (which is on the other side of the room and this room has a vaulted ceiling....).

Instead I'm thinking about putting a new 2" vent in behind the shower that feeds to the roof :

I'd like to minimize 2.125" holes in my 2x8 so am thinking of running the shower drain parallel to the joists and then down thru a lower level wall to the basement:

So is there a way to vent the shower arm before it drops down?

I understand "You can't run any dry vents for the second story fixtures in the second story floor joists." (Can someone explain the principles/thoughts behind this?) Would putting a horizontal wye in the drain line that then feeds back to a new stack venting thru the roof be acceptable? If not any other suggestions?

Thanks again

 

[Reach4]

NC uses IPC.

Wet vent of the shower often easiest, since the wet vent can be horizontal. Dry vent the lavatory. Run the lavatory drain (IPC: 1.5 inch or 2 inch) to wye into the side of 2 inch the shower drain pipe that carries the output of the shower trap.

If you want to use a separate vent for the shower, then you can run the shower trap output under that wall, and use a sanitary tee on its back to dry vent the horizontal drain pipe. To dry-vent the shower, the vent line must be within 45 degrees of plumb.

"Venting how?" : normally you would connect to another vent in the attic. An AAV is possible if the connection in the attic is not practical.

Picture shows wet venting of shower. Purple is vent to attic.
Pink is lavatory. Green and blue would be one alternative where green is in the wall, and blue is under the floor. Other alternative: yellow and orange would be another alternative where yellow is in the wall, and orange is under the floor.
With yellow and orange, venting would be via wye or santee on its back. With Green and blue, the venting would be via a santee.

 

[Jim_B]

Reach4 - thank you for the details - this makes sense and I'm inclined to go the yellow and orange, wet venting wye approach.

However, you also said something that interests me:

"If you want to use a separate vent for the shower, then you can run the shower trap output under that wall, and use a sanitary tee on its back to dry vent the horizontal drain pipe. To dry-vent the shower, the vent line must be within 45 degrees of plumb."
​

1) If I did this isn't considered a dry vent within a floor joist because it directly goes vertical up thru the wall and out the roof?

2) I could put an AAV on the lavatory - but could that AAV be used to vent the lavatory and also wet vent the shower?

 

[wwhitney]

1) Correct. My comment should have included the word "horizontally". To partially answer your earlier question, dry vents can't go horizontal at lower than 6" above the flood rim of the associated fixture. I assume that's so in the event of a backup, water is kept out of the horizontal vent section by spilling out of the fixture. You don't want any solid transported into the vent by the backup, which could subsequently block the vent, defeating its purpose.

2) Yes. With a horizontal wet vent, the shower trap arm is the pipe segment from the shower p-trap to the horizontal wye where the shower and lav join. As long as that trap arm falls no more than one (internal) pipe diameter, and the lav is dry vented (through the roof or via an AAV), then the lav wet vents the shower. [Assuming a reasonably direct routing of the lav drain.]

Cheers, Wayne

 

[Reach4]

Using the red-yellow-orange path, the method can vary. My depiction of the trap in red could be misleading; it was somewhat schematic. There are various options of handling that area. Outside walls are generally structural.

1) If I did this isn't considered a dry vent within a floor joist because it directly goes vertical up thru the wall and out the roof?

Yes, that would be a dry vent. The lavatory would have its own dry vent.

You could join 3-inch toilet waste with either of those and that would wet vent the toilet. Interest you in adding a toilet while you are at it?

The method shown in this video may or may not be of interest. Even tho you are not using concrete, it could be useful in locating that shower drain if you are doing your piping before dropping the base for the last time.

 

[Jim_B]

Reach4 - Thanks for sharing your knowledge - my next steps are coming into focus (and they don't include a toilet or any additional complexities ).

Appreciate the YouTube 'make a template' video. I had 'permanently' hung a plumb bob from the ceiling - but I like the template idea as well. Thanks again