DWV Horizontal Layout and Venting Help

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CAdamL

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New Stack and first floor plumbing for double bath. A lot horizontal to horizontal venting I could use some help with, would like to wet vent portions of it to cut back on back venting due to limited access into and out of walls, am in the trades and know my way around plumbing but not real familiar with so much horizontal branches and tie in. Any help, suggestions and feedback would be greatly appreciated. Everything I have now is just dry fitted and subject to change, one of the constraints is head room in basement hence everything trying to be kept in joist bays, no clear run for straight stack hence the vertical to horizontal main and horizontal branches. Could get lavs and tub and shower back vented above 42 pretty easy but my Wc are almost impossible to vent without wet venting. Have some 1 1/2 that would need to be changed over to come into compliance with the wet venting but no big deal. I am under. IPC so under wet venting I believe wcs can be either down stream or up. If anybody has time to look and maybe help with my best options, guidance and advice it would be appreciated
 

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JG plumbing

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When I've plumbed Prefab houses where everything is stubbed into the basement (which this is very similar to) we have to vent with a tee looking up and then drill through a joist or two into a dry vent (which I think would be your vtr). But if you can vent more traditionally into walls you should do that. Cut in clean outs so you can service things as conveniently as possible, even the vents that can't be traditionally vents.
 

JG plumbing

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I think i would raise your vtr pipe as high as you can and try to vent into it from the other horizontal lines. Try to leave the drainage piping as low as possible and the vent up high. You may need to roll the tees onto a 45 and then street 45 to save height.

That's if I'm seeing what I think I'm seeing.
 

CAdamL

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I think i would raise your vtr pipe as high as you can and try to vent into it from the other horizontal lines. Try to leave the drainage piping as low as possible and the vent up high. You may need to roll the tees onto a 45 and then street 45 to save height.

That's if I'm seeing what I think I'm seeing.
I think i would raise your vtr pipe as high as you can and try to vent into it from the other horizontal lines. Try to leave the drainage piping as low as possible and the vent up high. You may need to roll the tees onto a 45 and then street 45 to save height.

That's if I'm seeing what I think I'm seeing.
Thanks for the feedback JG. I totally get where your going with my vtr and bringing horizontal branches in and that would be doable except technically right now it’s a dry vent and IPC says no horizontal dry venting until your above 42 inch flood rim, I can tie into it with my back venting but below you have to stay at atleast at 45 until you tie in, and it’s currently as high as she will go but regardless if I use it as dry vent I have to tie in up top. Another scenario is if I was to bring my branches over as drains and wet vent that horizontal section of vtr I am within distances except wcs might get one wc in on it within the distance of wet venting, but then the catch is according to IPC and kind of a debate depending on who you talk to, on a horizontal to horizontal wet vent you have to come into it at true horizontal you can’t be above it and wye into it, so I would have to drop that 3 inch vtr about 7 inches to have it come into my horizontal main, which puts it way down below joist. Like I said I can realistically even with my constraints which are like tripple and quadruple joist siting on first floor wall with headers everywhere and more tripple joist running opposite running opposite way, I literally have two walls out of two baths I can get into and out of with pipe but I can get lavs shower and tub all back vented into my vtr it’s the wcs that I am having a hard time staying vertical with until flood rim. Or am I missing something obvious.
 

JG plumbing

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So the reason for the 42 is, in the event of a plug downstream, the vent won't become plugged. That's where the clean outs come into play.

Your local inspector is who you want to consult to ask whether or not they will accept what you want to do. They pass the scenario I described in my area, becuse it's accessible for maintenence and the houses are finished with no way to realistically correctly vent.

Is there a reason your using ipc? I'm not as familiar with it as we use upc. There should be a combination vent scenario that you could use if you/the inspector prefer.

To me I see a way to raise the vtr. You'd have to change fittings you don't need that wye a tee would be fine.

Keep in mind I'm not there and can't look around and get exact spacing or measurements nor get a100 percent perspective through this forum.
 
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JG plumbing

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After some re rereading and recalling (I think ipc differs from upc quite a bit on trap arm length) I think i would totally reconfigure your piping. Lol sorry I know it's crappy advise (as in advise you don't want to hear). To me it looks like you should be able to change the piping and get a sytem that works well, does what you want, and passes code.

Being a free advise site I might get some time to sketch it for you... But I might not. Maybe someone else will jump in and help. I just don't have the time right now. Sorry I know it's a little unsatisfying.
 

CAdamL

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Thanks JG for feedback, and yes we are under IPC in my state. They do allow a pretty good length in the trap arm I think it’s like 6 feet on 1 1/12 and 8 feet on 2inch, so their is room to maneuver in that sense. Originally had a good layout and then things got changed and addded and changed again with new restrictions, to the point I have probably overthought it. Would have to ask inspector about the vtr, thanks for the feedback and like I said everything is only dry fitted right now and I got room to change things around as need be, I know it’s a free advice sight and I greatly appreciate your input, but if you have a clearer picture or are seeing something I am missing and did happen to find time to sketch something up it would definitely be welcomed and greatly, greatly appreciated and could be worked out, because at this point i just really need a fresh outlook and opinion.
 

JG plumbing

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My guess is there has to be a wall you could get up into from the main horizontal run that you have everything draining into. If you could get a 4x4 or even a 4x3 tee into the main looking straight up into a wall, you could do a combo system. You just need to upsize the branches. You would likley have to make a soffit of some kind if you use 4"for this. I'm not sure how much is finished above.
 

JG plumbing

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Or you flip it and use the vtr pipe to drain the nearby fixtures. Being remote and figuring everything isn't going to be ideal. I'm sure there are many things I cannot see, mainly what's above.
 

JG plumbing

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Also if I remember right toilets or similar fixtures with the trap above, by necessity need a portion of the vent to be horizontal. Im pretty sure the code references that by with some language that allows for as much.
 

frodo

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You can not do what you are trying to do
You are not going to be able to hor. wet vent with out drilling joists

My suggestion is drill the wall and bring vents up.

coil2.jpg
 

CAdamL

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You can not do what you are trying to do
You are not going to be able to hor. wet vent with out drilling joists

My suggestion is drill the wall and bring vents up.

View attachment 29119
Thanks for feedback and taking a look Fredo and JG So you are absolutely correct I tried today to get things to line up to wet vent that main 4” but impossible I have to drop all the branch arms so far to meet up at horizontal or even less than 45 that it was futile. So I kinda started looking in the direction you and JG were getting at. I can get both lavs back vented from up top and the shower fairly easy, tub also with a little finagling I think and get them tied back into my 3”vtr up top. And I don’t mind drilling the joist in basement to bring a couple together and wet it in that horizontal section you depicted in diagram, the only problem is and i was looking at it tonight, I would have to bump those wetted lines up to 2” and all my walls are 2x4 only 2x6 wall I have is may tub/lav divider wall which my second floor stack and 3inch vtr run through, my drain snd vent size both have to be two inch on a wet scenario right.? And my farthest fixture upstream is one of my lavs that’s to far to have it wet anything so I could stay regular their might have to double up a couple studs for the others, because it’s not straight up shot literally have a quadruple joist sitting on top plate but my bottom plate would still only be 2x4? I guess my biggest problem is tying in my 2 wc they are both just in a horrible spot.
 

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JG plumbing

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Find somewhere to go up with a 2" vent in between the two wc's in my sketch. If they are too far apart you need two vents for the wc's.
 

CAdamL

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You can not do what you are trying to do
You are not going to be able to hor. wet vent with out drilling joists

My suggestion is drill the wall and bring vents up.

View attachment 29119
Thanks again for the advice and feedback, greatly appreciated. So after going back an reading post and looking at your diagram i might have confused what you were saying, but correct me on any misinterpretation but I think you were saying if I was willing to drill joist I could wet vent in that horizontal section and bring a couple things together and save a little venting again upsizing line and 2x4 walls becom a factor, it would be nice to have a little more space on the main connection with one or two less wyes to tie in everything is so close together or just individually back vent everything which I think I can do and have figured out especially if I don’t have to upsize lines up top be a little crowded on my tie in with eyes on main but I could make it work. Here is my thought on the wc in my pic the one to the left you can see is off set out in front of my main 4” horizontal by about 7” the one to the right is off set the same but directly above stack, thinking of running separate line tying them together and dumping into stack separately? One to left I can get vented, one to right maybe with a little finagling but I would have no trap arm it would just dump in, not sure what IPC says about that, I have to go in and get a read on it. I hope I am making sense and atleast somewhat on the right track? Thank you again for advice and guidance.
 

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CAdamL

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Find somewhere to go up with a 2" vent in between the two wc's in my sketch. If they are too far apart you need two vents for the wc's.
Ok so we were definitely thinking along the same lines for the wcs and I can get a vent up almost in the middle of them, now I am taking a 2” vent into a 2x4 wall bottom plate whatever inspector would just have to deal with but to get out of that wall because theirs a quadruple dormer truss/joist sitting on top of it I would have to come across stud bays you can double up twice after that you can’t cross any more I think I need three bays to get across were I could feasibly go up. But it’s looking like I might have to go with that scenario and just figure it out actually under IPC i think I can vent with 1.5 think only upc uses 2”, weather I can use one 1 1/2 for both or have to vent individually not positive. But either way the setup and idea is best solution. Thanks for sketching out, the only problem I see or would be worried about tying into the vtr below is it’s technically a dry vent IPC says no dry venting horizontally until your 42 flood rim, any dry vent being taken off a fixture down below has to stay at a vertical rise until you reach 42, and any way I connect to the vtr I still have a horizontal section of vent before it rises unless I dumped something into up top and then its wet and then my connection to my main has to be horizontal to horizontal, curious to know your thinking on it because maybe I am not interpreting it correctly. Either way I could bring a couple things together and wet them in that small horizontal section or just back vent them individually. Seriously thank you for taking your time and knowledge to help, greatly appreciated.
 

JG plumbing

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So from the traps to the riser on the vtr is your trap arm on each of those two (or three actually cause I left out the lav) there is no horizontal run of vent. You just have to have the vtr piping large enough to vent both (or all three actually) and drain. Upc allows combination vent /drain which is different than a wet vent. The distances have to be right and the sizing too.
 

CAdamL

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So from the traps to the riser on the vtr is your trap arm on each of those two (or three actually cause I left out the lav) there is no horizontal run of vent. You just have to have the vtr piping large enough to vent both (or all three actually) and drain. Upc allows combination vent /drain which is different than a wet vent. The distances have to be right and the sizing too.
I would just be cutting out the wet vent section of that!? Then it would just be a matter of pushing that vtr up as high as I can in the bay to bring my branches in and keep them in bays. I could switch all lavs over to two inch drains and tub two inch, two inch trap with bushing ? or 2 line with 1 1/2 trap. Either way I could get a few lines in on it and I’m 3” for what at most 5 or 6 dfu. And I think I can do both wc with one 1 1/2 under IPC.
 

JG plumbing

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The red portion of the picture above is "wet vented" the main is your "vtr" pipe.
 

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