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Homeowner here. Finishing a large basement, including a big master bath. Builders roughed everything in under the slab, and I framed it and am running electrical. Was planning to hire the plumbing, but between the quarantine and plumbing estimates I got, I'm considering doing it myself. I've posted a couple photos and will describe my issues below. Would appreciate advice and how you'd vent and run water to the lavs in this setup. Thanks!

1) Builder put a main HVAC trunk directly above lav 2. I dropped the ceiling to just barely below it while framing, but I hadn't considered plumbing at the time. Trunk extends out several inches on either side of the header, so vents and PEX lines to lav 2 can't come straight down. Either they need to run through the framing on either side or I need to frame a bulkhead on the wall behind the bathroom. That area is like an entryway or sitting room with entrances to the master bedroom, bath, and a closet.

2) Builders left a capped 1.5" vent above lav 1 and another on the far side of the basement about 25 feet away -- perhaps for lav 2. It's near the ejector pit, but that already has its own capped vent left on the wall right next to the waste line. Can both lavs (and by extension, the whole bathroom -- two lavs, toilet, and separate tub and shower drains) be vented by the line above lav 1? Either way, how would you deal with that stupid HVAC trunk above lav 2? Can a 1.5" vent line realistically be run through the framing above the doorway there to serve lav 2...or is a backside bulkhead a better idea?

3) Builder left 3/4" PEX stubs above the toilet and shower, but none above either lav. There are 1/2" lines running in the joists above lav 1, I believe from the laundry to the kitchen on the main floor, but no stubs left. Would you tap into that 1/2" line to supply one or both lavs, or would you tee off one (or both) of the sets of 3/4" stubs that were left elsewhere in the bathroom? And again, given the obstacles around lav 2, how would you run those lines? Parallel to the vent after figuring that out?

Thanks for any advice!
 

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Can you tell me what plumbing code this work was done under?

I'd bring the vent out of the wall. Drilling that many holes horizontal can get messy...

By upc code, the toilet would need a minimum 2" vent. The remaining may or may not fit on a 1-1/2" vent- you are pushing the DFU sizing and I don't know your exact DFU count.

Same with the water. The 1/2" lines sound like they are used upstairs tot he point you should not add to them. Use the 3/4" lines to serve the base ment load
 
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Discussion Starter · #3 · (Edited)
Can you tell me what plumbing code this work was done under?

I'd bring the vent out of the wall. Drilling that many holes horizontal can get messy...

By upc code, the toilet would need a minimum 2" vent. The remaining may or may not fit on a 1-1/2" vent- you are pushing the DFU sizing and I don't know your exact DFU count.

Same with the water. The 1/2" lines sound like they are used upstairs tot he point you should not add to them. Use the 3/4" lines to serve the base ment load
Thanks for replying! I live in Indiana, and Google tells me they follow IPC with a few amendments. Everything under the slab was inspected prior to me taking ownership, and I've been told by multiple plumbers who bid the job recently that everything is vented by the lavs. I was only left 1.5" vents in the joists as mentioned, so I'd love your opinion on whether/how that works.

It was suggested on another forum that I perhaps could vent "Lav 1" directly up to the capped vent in the ceiling and use an AAV on "Lav 2" given the difficulties accessing it. I'm already planning to use an AAV on a bar sink in the basement, and I also wasn't sure what's being wet vented by that lav 2. Just wasn't sure if an AAV would be allowable.

For the water lines, how would you suggest I split the load? There's four stubs left: a set of hot/cold above the toilet and a set above the shower (each 3/4"). Obviously one cold straight down to the toilet. Could that set of stubs serve one of the lavs with the other handling the shower, tub, and other lav?

Seriously appreciate the reply!
 

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I can't help much with IPC code. I work with UPC. IMO, UPC over does the venting of fixtures. Where IPC seems to do too little....
@Ghostmaker is a IPC inspector and knows his stuff. If he wanders through, he'll set you straight.

My state does not like AAV's and allows them in limited locations. So, again your local plumbers will know this. Using one on the lav as you suggest may not be good if that is also venting fixtures downstream.

As for water, it is a rule of thumb to put a maximum 2 fixtures on a 1/2" line.
With high water pressure and low gpm flow fixtures, IMO, you could stretch to 3 fixtures if needed...
 

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Okay, I went back and looked at the duct work above the lav. It looks like you have 1-1/2" drywall backing and 3/4" strapping. That equals 21/4". This means you need to gain 1/4" to roll a 90 out and around the duct. Can you push the duct up that much?
 

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Discussion Starter · #7 · (Edited)
Where is the toilet in all your pictures I see one lav drain in a wall and a door in the wrong place because it blocks the lav on that side. Show me the toilet drain the shower drain.
Thanks for asking. Below is a photo I already had with arrows to all the drains. I also decided to quickly sketch it as it's hard to get a photo with everything.

Two lavs with the door between them. Both will be 48" vanities, not quite centered but close. WC is on left side and has a 4" drain sticking up through the concrete. Shower is next arrow to the right in that 38 x 60 enclosure, then a drain for a freestanding tub that will be filled off that same wet wall.

Hope that makes sense. If I need to take another photo and actually write on it I can do that. Appreciate you both weighing in.
 

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Okay, I went back and looked at the duct work above the lav. It looks like you have 1-1/2" drywall backing and 3/4" strapping. That equals 21/4". This means you need to gain 1/4" to roll a 90 out and around the duct. Can you push the duct up that much?
Thanks for that! I just tried, and it does look like there's just about that much play with the vent -- 1/4" maybe. So from what you've seen, is that what you'd do?
 

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Yep, if you need to get the vent out of the wall and don't want a soffit.
Notch out 21/2" sq hole for the 90 to sit in, looking towards the toilet. Run horizontal until you clear the duct and then go up, drill the joist if needed to get to the existing vent.
I don't believe IPC has any restrictions on how many 90s you use in a vent. (UPC doesn't)

BTW, those are interesting joists. I assume you can drill those?
 
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Yep, if you need to get the vent out of the wall and don't want a soffit.
Notch out 21/2" sq hole for the 90 to sit in, looking towards the toilet. Run horizontal until you clear the duct and then go up, drill the joist if needed to get to the existing vent.
I don't believe IPC has any restrictions on how many 90s you use in a vent. (UPC doesn't)

BTW, those are interesting joists. I assume you can drill those?
Thanks again -- you've been incredibly helpful. I think I'll follow your suggestion and give that a shot! It might be a couple weeks since I'm finishing up electric, but I'll report back.

Nice eye catching the joists! They're actually "fake" joists I created to drop the ceiling by a foot in a good portion of the basement. They're 8' sections of 7/16 OSB cut to 12" each (so 4 out of a full sheet) with 1x2 screwed on top and bottom. They're attached perpendicularly to the actual joists above. Super light but rigid, and perfect for someone working along. Got the tip on a YouTube video about soffits/ceiling obstacles. Some people space them exactly 16" on center and use it for drywall, but I had a ton of HVAC and plumbing obstacles so I placed them where I could and then used strapping for the drywall.
 

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Yep, if you need to get the vent out of the wall and don't want a soffit.
Notch out 21/2" sq hole for the 90 to sit in, looking towards the toilet. Run horizontal until you clear the duct and then go up, drill the joist if needed to get to the existing vent.
I don't believe IPC has any restrictions on how many 90s you use in a vent. (UPC doesn't)

BTW, those are interesting joists. I assume you can drill those?
Wanted to report back and say I finally got around to doing this today according to your suggestion and it worked beautifully IMO! That 90 under the HVAC trunk definitely makes contact with it, but it's heavily insulated everything I read tells me it won't be an issue. Hope you agree! Anyway, thanks again for the assistance.
 

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