I've added a master bath onto my house. I've sketched up the diagram below for the vent and drain system. While it's not exactly to scale there's crawlspace room to accommodate it, and the floor joists run parallel to the drain lines from toilet/tub/shower traps to drain line so this could be achieved without cutting joists.

I live in South Carolina and my local permit office has the IPC plumbing code on hand for reference. The distances as marked between the trap weirs and vent are overstated by 3 to 5 inches (meaning the actual distance is slightly LESS than the 6' and 5' measurements listed). I'll use mostly combo tee/wyes for the connections.

Are there any issues/problems with the system as drawn relating to pipe sizing/venting or distances from trap to vent? I realize the 2" vertical vents and 3" horizontal line for the tub/shower/sink is overkill (versus 1.5" vents and 2" drain) but I have those PVC pipe lengths on hand and would like to try to utilize it if possible (i.e. budget reasons).

Thanks in advance for any constructive comments/feedback.

Wow! Are you sure you don't live in California where they vent everything including the family dog. Your code and mine aren't too far apart, Here's how we put our bathrooms in.
I assume wet vents are allowed in your local code, Let me know if this would work for you, Regards, Tom

LOL... no, definitely not in California. Wet vents are allowed here. I'm not sure your drawing would work for me - while I think I could remove the vent for the tub (since it would be wet vented by the shower vent) I think vent run for the shower would have to stay. If the shower drain were at an angle over to the sink vent it would be too far a run. For a 2" line the max distance to vent from the trap weir is 8' if I'm reading that correctly.

I live in a municipality that allows homeowners to act as their own builder so long as the work is up to code. If I choose not to do some portion of the work myself I can hire a licensed professional (as I'm doing with the electrical portion). Anyway I've noticed that the inspector is a little more "thorough" on homeowner work versus work done by the professional. So while my plan is definitely overkill I don't want to leave any doubt that each fixture is properly vented without any possible flat vents or "missing" vents (even if they're wet vented). As mentioned I have the 2" and 3" PVC on hand so it's no extra expense in that department.

I suppose I should clarify the difference between my layout and yours - the toilet, tub and shower are on one wall while the sink is on the opposite wall like this sketch. Bathroom is approx. 14' long and 7.5' wide.

These are drains in red aren't they? How about moving the drain line more towards the center of the room to reduce the length of the fixture drains? Would that work for you? Cheers, Tom

Yes, the red represents the drain lines. You mean like this, with the sink vent remaining in place and serving as a wet-vent for the shower, tub and toilet? I think that would leave the shower within the 8' trap to vent range too.

Then run a separate vent for the shower. Your original vent layout was just dandy. I was simply trying to save you some work. Regards, Tom

I'm a little confused... with the modified drawing above I think the shower would be within the required 8' limit from trap to (wet) vent. So you're saying I'd still need a separate vent for the shower?

I do appreciate the help, Tom. Many thanks for hanging in there with me.

My bad! You're correct. Would you have enough fall to drop the lav drain and the line it connects to allow both the tub and shower to run over the 3" drain and 45 into the lave drain separately. I can see a problem combining the tub and shower drain. What are your thoughts? Tom

I don't know about combining those drains... I'd have to dig into that part a little bit. I could see where that drain line between the shower trap and the tub connection could be a problem, like if the tub were filled and then drained would the rush of water in the line create some siphoning action and want to suck the water out of the shower trap? Maybe the tub needs to connect to the wet vent AFTER the sink connection rather than before it.

I also need to see if wet venting the tub, shower and toilet off that one line are okay. I presume it is since they're all on the same level.

I appreciate the help; it at least gives me some direction. I might sketch up the modified version as well and take both to the local permit office and get their thoughts. I think as a worst-case scenario my initial drawing, while overkill, would certainly meet code for venting and draining the fixtures properly.

Many thanks again for the help.

Your last drawing had the unvented shower draining past the tub and the suction could siphon a trap. Now if you could figure out away fore both the tub and shower to connect back to the lav drain at separately points I believe you could vent your bathroom group with just one vent. And you're absolutely correct. The inspector would love your first layout. Let me know how you make out. Tom

Thanks Tom. How about the sketch below, utilizing some 45* bends and wye fittings to get the tub/shower vented? So now the shower has a less than 8' run of 2" pipe before meeting the wet vent and the tub drain connects after the lav vent. So now it seems any discharge from the shower will draw air from the lav vent as will the tub discharge.

Looks good to me. Run it by the inspector. Good luck, Tom

Hi guys. I like the first drawing. Can't really go wrong this way. There is no such thing as too much venting, but you can run into trouble with under venting and wet venting if it isn't done correctly (at least by code standards). I say stick with your original plan, or better yet, let the plumber you hired do it the way they do it and deal with the inspector. Take care and please let us know how everything works out.

I agree with Dad. Ya just can't have too many vents. What you can have ,however, is overkill. And that's what I think he has in drawing #1. Regards, Tom

Thanks for the feedback. I'm going to sketch up the second wet-vented plan and run both drawings by the inspector. There's no hired plumber here (I'm it) so I want to get the permit office's approval on the work I plan to do in advance to avoid any later concerns they may have. I agree with you on the "never too much venting" part but I want to cover all the bases. Plus my real concern in all of this is the distances between the trap weirs to the vents. Given that my municipality follows IPC it seems as if I'm right up against the max distance from trap to vent on some of the fixtures or having the needed slope exceed the pipe diameter. That's part of the reason I'm using a 2" drain line on the tub where 1.5 would normally work on my initial drawing - at 1 slope of 1/4" per foot over a 6' distance is 1.5 drop. The same would apply to the shower in the new sketch utilizing the wet venting I'm afraid the shower trap to vent distance is a 2" slope (1/4" drop over 8' = 2" slope). While all of these meet the "minimum" standards I'm not sure I want my new master bath to be done to the "minimum." And according to the 2006 IPC the distance from the trap to vent for self-siphoning fixtures (like water closets) is unlimited. I can't seem to get my head around that it doesn't matter if the toilet is 1' away or 20' away from the nearest vent.

I'll update this thread with what they say once it's done. I do appreciate the comments and help I've received here.

In case it's not obvious I'd also like to mention that in this layout the toilet, tub and shower are all located along an exterior wall. I think this could be made a lot simpler if a vent line could be located closer to those fixtures on that wall but I'm not real keen on notching rim joists and load bearing plates to get those lines in there. Plus I'm not certain that's allowed.

Maybe something like this where the tub/shower share a vent?

Maybe something like this where the tub/shower share a vent? All your fixtures share a common vent, however the shower's wet vented by the tub. Is that the way you wanted it to play out? Tom ,