Will my plumbing remodel work (horizontal wet vent)?

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hbarkley

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Hey everyone,

I'm at the plumbing stage of my DIY master bathroom remodel. I have some questions/concerns with how I've organized the layout for the fixtures. The information is in the pictures below. For reference, I live in North Carolina which I believe follows the IPC.

before.png
proposal_a.png
proposal_b.png


I'd prefer to go with Proposal A. But if I have to upsize the wet vent, then I've added another Proposal B to consider. I've added AAVs to vent the new sinks because that wall is load bearing and has some structural framing in the way of any potential roof vents.

Please let me know if either/both would work. Thanks!
 
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Jeff H Young

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the wet vent is sized by the drains running through it the w/c dosent run through it . so you got 2 lavs and a shower isnt that 4 fixture units?
 

wwhitney

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Jeff's right.

The remaining issue with your diagrams is the former wet vent upstream of where the shower is now tying in. With no fixtures draining into it, it's now a dry vent. Which can't be taken off flat like that. So you should remove the 2" pipe upstream of that point. The shower trap arm is measured from the shower trap outlet to the point the first dry-vented (via an AAV) lav comes in to join it. If it's now over 8', you'll have to adjust your design (e.g. use option B).

Cheers, Wayne
 

Jeff H Young

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The dry vent needs to go away proposal b looks OK, the lavs can be wet vents. Don't know if AAV will fly (code)
 

hbarkley

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Thanks guys for the replies. Seems I misinterpreted the code for the wet vent sizing, and I'm glad I asked about it.

I updated the proposals below based on the feedback.

proposal_a_v2_final.png
proposal_b_v2_final.png


For the new Proposal A:
  • I moved the shower line close to the back of the room so that the dry vent can take off close to vertical. (Seems like an angle greater than 45 should be acceptable?) Moving the shower line farther back would work out OK for my plan anyhow since I'm planning to use a linear drain for the shower placed against that far wall.
  • This feels like a more robust venting solution for the toilet. I feel like solely venting the toilet through the lav's AAV is asking for trouble. I'm assuming, in this updated proposal, would the toilet now vent through the dry vent again? Or still pull from the nearest AAV? In any case, I'm assuming the dry vent provides an extra vent to the toilet if the AAV fails, or would the toilet just siphon the lav trap if the AAV fails?
For the new Proposal B:
  • Not as big a fan of this proposal, as mentioned above, because I'm relying on the AAVs to vent the toilet.
And both plans rely on whether or not AAVs are up to code. I didn't see anything in IPC 918 that jumped out at me that states they're not allowed, but I'm also not familiar with a lot of the language.
 

Jeff H Young

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a depends on the code b depends on inspector finding hardship and alowing the dry vent
 

wwhitney

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hbarkley

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Cool, I think I can do that. I took a picture of the current plumbing and drew on top with the proposal for A. Moving the shower line one joist bay over and then having the vent come out of a wye + 60. I'd have to notch another hole in the bottom plate but that's no problem.

proposal_a_vent_plumbing.jpeg


I think ideally I'd move the start of the wye/vent over to the left one stud bay so that I don't have to turn the drain 180. That would mean I would need the start of the vent to be 1.5" so that it is narrow enough to cross the middle of a 2x4 stud. The idea is that the vent would be 1.5" until it crosses the stud and can be joined into the 2" vent.

As far as I can tell, it's OK to reduce the size of the vent from 2" to 1.5". The 1.5" vent size should be enough for the drain line so I think I'm OK?

a_vent_option2.jpeg
 

wwhitney

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I'm not clear on the rules, if any, about just upsizing the vent in the middle of a run. A 1-1/2" vent is sufficient under the IPC for a 3" drain.

You definitely don't want to do the U-turn you drew. For the early take off, you'd want the vent to rise in the stud bay to 6" above the flood rim of the associated fixtures, then turn horizontal and penetrate the stud perpendicularly. For a single stud, I think if you doubled it and drilled a centered 2-1/2" hole (for a 2" vent), you could reinforce it with a Simpson Strongtie HSS2-2-SDS3.

https://www.strongtie.com/miscellaneousconnectors_woodconnectors/hss-ss_productgroup_wcc/p/hss.ss

(Maybe doubling is overkill and you just use the single stud version). I'd suggest some sort of stud shoe even if you only drill a 2" hole (for a 1.5" vent), although if I recall doubling the stud allows you to drill it up 60% of the width.

The other option is to take off the vent in the desired stud bay (using a san-tee on its back if that works better), then turn and drill a new hole through the joist, and then jog in a joist bay with a pair of 45s (better than a pair of 90s). That existing hole in the joist looks suspiciously low, there's supposed to be 2" of undrilled wood at the top and bottom of each joist. So in the event that some of your joists need repair, you may end up being in position to drill new holes where you want them. What is the joist size?

Cheers, Wayne


 

hbarkley

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OK, I feel pretty good about keeping the vent at 2" once I can get my hands on those stud shoes. And I have no problem doubling the stud there too for some extra security. I now consider the venting aspect a problem solved.

Here's an updated sketch:
vent_3.jpeg


Is this what you mean by "jog in a joist bay"? Hadn't heard that term but from what I can gather it's re-routing a section of line.

Regarding the floor joists:
I have 2x10 floor joists. I don't have a problem with drilling a new hole for the line. I'll actually be sistering a new full-size joist onto this one. In fact, it's the last joist in the room that I haven't sistered a new one to. The purpose of the new joists wasn't necessarily for strength. It was instead to bring the floor to level (the floor dropped about 1.25" over 10'). But I'll make sure to remove the pipes first so I can sister on a new, non-notched joist for added strength. This should give me the freedom to bore a new hole wherever I need.




Side note: In retrospect, I should've removed all of the plumbing before sistering any of the joists so that I could have avoided having to notch around the existing (yet soon to be removed/re-done) pipes. This would've saved me some time and not compromised the strength of the new joists. This has been a bit of a learn-as-you-go experience though and in the end it didn't matter because I didn't need them structurally.
 

wwhitney

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Is this what you mean by "jog in a joist bay"? Hadn't heard that term but from what I can gather it's re-routing a section of line.
What you drew is fine. But just using a straight segment and then a LT90 would let you drill the joist perpendicularly, rather than at an angle. And I don't see any particular advantage to using two 45s.

What I meant by "jog in a joist bay" is this: say you didn't want to drill the stud , you use a san-tee on its back for the vent takeoff as far left as possible for the desired stud bay, then a street LT 90, but now you are hitting the joists too far to the right to line up with your existing pipe. Drill the first joist lined up with the LT90. Then immediately after the joist, put on a 45 to start jogging. Then put on another 45 when you are lined up with the existing joist. Hopefully that would all happen in one joist bay, otherwise, you'd have to drill the next joist at a 45 degree angle.


Side note: In retrospect, I should've removed all of the plumbing before sistering any of the joists so that I could have avoided having to notch around the existing (yet soon to be removed/re-done) pipes. This would've saved me some time and not compromised the strength of the new joists.
It's not too late to do this over. I hope when sistering you used kiln dried material, to avoid any effects from new wet lumber shrinking relative to old dry lumber.

In particular, if you have any joists where a hole is closer than 2" to the top or bottom of the member, or it has a significant notch, I would say it is important to add an unnotched sister to those joists.

BTW, if your only purpose was to level the floor, rather than strengthen/repair the joists, 2x4s would have been sufficient.

Cheers, Wayne
 

wwhitney

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PS The maximum prescriptively allowed hole in a 2x10 is ~ 3-1/16". So wherever you have a 3" DWV passing through a 2x10, you'll need a metal repair bracket.

Cheers, Wayne
 

hbarkley

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What you drew is fine. But just using a straight segment and then a LT90 would let you drill the joist perpendicularly, rather than at an angle. And I don't see any particular advantage to using two 45s.

OK, great. I see what you're saying now about jogging. In any case, I feel like I have the information I need to get started and will keep this in mind. Thanks a ton for the detailed responses.

It's not too late to do this over. I hope when sistering you used kiln dried material, to avoid any effects from new wet lumber shrinking relative to old dry lumber.
This is great advice. Yes, I used KD lumber and I made sure to test each member with a moisture meter before install, too.

In particular, if you have any joists where a hole is closer than 2" to the top or bottom of the member, or it has a significant notch, I would say it is important to add an unnotched sister to those joists.

BTW, if your only purpose was to level the floor, rather than strengthen/repair the joists, 2x4s would have been sufficient.

The joist pictured is really the only one that has suspect notching/boring. I"ll definitely be using a full-sized sister joist here. Otherwise, all the other bored holes look up to code; so the other sistered joists weren't necessary structurally.

As for the leveling, yes I realize I could've used smaller dimension lumber to accomplish this. Given the recommended nail pattern, I could've gotten away with 2x8s or maybe even 2x6s. I ended up deciding to go with full-size 2x10s since the difference in cost wasn't that much. I figured I might as well make the floor as strong as possible while I have open access to it.

In all, I'm confident with the way the floor leveling/sistering turned out so far. No, it wasn't totally necessary but the floor feels a heck of a lot stronger and I can already feel that there's less deflection.
 
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