# Horizontal wet/dry vent question



## enjoytab

Hi, question about horizontal wet venting under the UPC. 

At the point along the horizontal soil line where the wet vent begins, is it illegal to roll that fitting at a 45 degree angle or on it's back? I've seen that before, where a 2'' WC vent is ran as if it is a standard horizontal dry vent, with the bottom of the vent opening above the centerline of soil pipe, but it is then turned into a wet vent by the bathroom lav. All the illustrations for horizontal wet venting show the beginning of the wet vent coming off flat, so wondering if rolling the fitting up is illegal or simply not mentioned. 

In general I guess I also don't understand why a dry horizontal vent requires the invert of the vent to be above centerline, but a wet horizontal vent doesn't. It just looks weird. What is it about making the vent wet that lets you keep the fitting flat, or am I misunderstanding a larger concept?


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## The Dane

I'm not sure I understand the question. Here In ND under upc we have to roll up the wet vent and no dry vent can be run horizontal until it is over 6" over flood rim level. In MN where they just this year adopted the upc they want the wet vent run flat not rolled up. 


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## rwh

I am not under UPC or IPC. Here wet vent comes of side, dry vent off top


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## bdaltonph

enjoytab said:


> Hi,
> 
> In general I guess I also don't understand why a dry horizontal vent requires the invert of the vent to be above centerline, but a wet horizontal vent doesn't. It just looks weird. What is it about making the vent wet that lets you keep the fitting flat, or am I misunderstanding a larger concept?


A wet vent is washed by the fixture, which is why it can enter the drain flat. A dry vent is not washed by anything. So if it entered the drain flat it's possible it could get clogged over time. Not sure about the upc. I don't follow that code but a wet vent should be able to enter the drain at any point


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## enjoytab

We are allowed here to run a horizontal dry vent below flood rim with the fitting rolled up and drainage fittings used. It just seems weird that a dry vent needs to be rolled but a wet vent can be flat, but I guess the justification of the wetting of the vent keeping it clear over time makes some sense. 

All the fixtures in the bathroom group are supposed to be connected independently and laterally, in order to reduce interruption of airflow above the mean water surface, but I'm still unclear if that means rolling the fitting up on a wet vent is actually illegal. I'm leaning towards yes. 

The horizontal wet venting diagrams also just look a bit bizarre to me, I have to admit. I'd be worried an inspector would fail me if I took a 2'' vent horizontally off the run of a tee servicing a toilet, then picked up a shower and lav with that 2'' vent, even if it is legal. Seems like a neat and convenient way to plumb though too, just looking to see if anyone has any experience doing it this way.


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## ShtRnsdownhill

you save alot of piping with wet vents, I just got into the habit of running 2 inch for bath lavs tied wet vent into the WC..but I always try to swing the tee at a 45 or anything but flat to prevent anything from flowing back or blocking the wet vent...and dry vent 45 to 90 for the same reason..


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## The Dane

I'd be worried an inspector would fail me if I took a 2'' vent horizontally off the run of a tee servicing a toilet, then picked up a shower and lav with that 2'' vent, even if it is legal. Seems like a neat and convenient way to plumb though too, just looking to see if 
anyone has any experience doing it this way.[/QUOTE]

how about simply calling your inspector and talk to him about it so you can find out what he will accept and what he will not accept. 




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## enjoytab

While talking to the inspector is the obvious answer, it seems the most daunting. I often get a guy that barely wants to give me the time of day on the jobsite, it's hard to imagine calling one up and peppering him with obscure code questions. But yes, it's probably the best way. 
I use a IAPMO code book for the UPC, IAPMO has a number you can call with code questions and you can also request that they provide you with written clarification. I think I'll go that route first, hopefully they're willing to help. 

On a side note I get nervous talking to inspectors about the code, because of having to worry about stepping on toes and offending them if you have to suggest that their interpretation isn't correct. I'd like to have the maximum amount of information available first, because if you get in a disagreement with the inspector, you're only recourse is facts, you never win the debate arguing interpretation. But I also can't stand the idea of getting failed because the inspector doesn't know the code as well as he should, and it seems like once they decide something, it's hard to make them change their mind, so if I start that debate I want every fact available to prove my point if I'm actually in the right. Just the perspective I've developed, some may have had different experiences.


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## Plumbus

You are northern CA and so am I. Where specifically? I may know the inspector or department you are dealing with.


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## enjoytab

Plumbus said:


> You are northern CA and so am I. Where specifically? I may know the inspector or department you are dealing with.


Thanks. I am in Sonoma County, work often in Napa County and mostly deal with those two building departments. I'm not a contractor so my inside knowledge of a lot of this stuff is pretty limited. My understanding is that the Cal buiding code uses the UPC, so anything the UPC approves is okay, unless you have a specific local county building code that overrules it. Would you say that is true? 

My nightmare scenario is to rough-in a horizontal wet vent thinking I'm all slick with my awesome layout and then have to rip it out because the inspector thought different. When you look at the horizontal wet vent diagrams it kind of just looks like someone plumbed a shower/sink/toilet combo and forgot to vent the toilet and shower. So maybe I'm not giving my local inspectors enough credit but I'm nervous to do it in the field. And heck obviously I don't know the code with full clarity myself, I'm still unclear on what the UPC is telling me I can and can't do, so hopefully IAPMO can help on that end. My PHCC instructor had no idea when I asked him during my code review class last year.


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## moonapprentice

Here in WI, your 3x2 wye has to be on plain. If you rolled it up it is considered to be cutting the vent off for the toilet if the shower was running. 

With that being said, you can roll your 2" wye only for your lav.

3x2 on plain, 2" wye you can roll.

This is how I was taught, and some inspectors may agree or disagree with that even in my area.

It may be a grey area for "code" interpretation, but if you have a good understanding behind it, you can talk to your inspector about it and let him/her know your reasoning behind your intentions, and then see what they say and go with that. 

Like others said, just talk to the inspector about it, short sweet and straight to the point. Good luck.


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## enjoytab

Maybe I'm just psyching myself out but talking to the inspector seems like the hardest route in researching this. I mean obviously I can talk to the particular person who shows up to inspect, but at that point I've already installed it, and if they don't see it my way I'm ripping it out. With multiple inspectors for each county it's hard to know if they all read the code the same way, or who is going to show up on inspection day.


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## Debo22

Where I am the inspectors are in the office between 7 and 8am. You can show up in person and ask to talk with one of them, usually they will answer any questions for you.


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## A Good Plumber

Consider attending the next local IAPMO meeting and ask any question without feeling intimidated. Getting to know the inspectors by attending the meetings they attend, will strengthen your understanding of the codes and their interpretations.
Attending the meetings is free, usually includes a good lunch and in many cases includes a guest speaker.


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## Plumbus

Try sending your questions directly to IAPMO. 
http://www.iapmo.org/Pages/AskACodeQuestion.aspx


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## GAN

Plumbus said:


> Try sending your questions directly to IAPMO.
> http://www.iapmo.org/Pages/AskACodeQuestion.aspx


You have IAPMO and also the ICC. Along with the interpretation of the AHJ.


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## GAN

enjoytab said:


> Maybe I'm just psyching myself out but talking to the inspector seems like the hardest route in researching this. I mean obviously I can talk to the particular person who shows up to inspect, but at that point I've already installed it, and if they don't see it my way I'm ripping it out. With multiple inspectors for each county it's hard to know if they all read the code the same way, or who is going to show up on inspection day.


You hit that on the head. I think i t should be sectioned off so you can deal with more or less the same inspector in an area.

Believe it or not we are all human, make mistakes and sometimes have different opinions on interpretations. None of which help you guys in the field.


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## Michaelcookplum

Don't roll wye on wet vent, run 3" towards toilet and leave off 3x11/2 wye for tub, then 3x11/2 wye for lav, then 90 up to flange. Simple,easy,done! Use 3x2 if tub drain is more then 6'.
You can also just use one 3x2 wye and then 2x11/2x11/2 wye (flat still) to catch tub and lav

Don't roll wet vented wyes



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## The Dane

Michaelcookplum said:


> Don't roll wye on wet vent, run 3" towards toilet and leave off 3x11/2 wye for tub, then 3x11/2 wye for lav, then 90 up to flange. Simple,easy,done! Use 3x2 if tub drain is more then 6'.
> You can also just use one 3x2 wye and then 2x11/2x11/2 wye (flat still) to catch tub and lav
> 
> Don't roll wet vented wyes
> 
> 
> 
> Sent from my iPhone using Tapatalk




I wonder what code you use? Under upc wet vent is minimum 2" no 1-1/2" allowed. Upc also requires to roll up past centerline. Unless you like Minnesota use upc with special amendments such as running wet vents flat. 


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## Plumbus

If I'm not mistaken, in Napa and Sonoma, where Enjoytab is located, the inspectors, being combis, are responsible for more than just plumbing. It follows that they will be less than sure about the finer points of the plumbing code. If he gets something directly from IAPMO, he can use it as justification if flagged on an installation by his AHJ.


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## MindLost

Are you referring to rolling a drain that is being wet vented on a 22 or a 45? That is against code. All drains being wet vented must be on the same plane.

P.S- I couldn't find it in the code book, so it must have been included in a code update class.

P.P.S - Rolling a combo on its back should be legit, no? I mean the only reason you would roll a combo on its back would be to a fixture, so that fixture would be going out the roof in one way or another right?


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## GAN

Illinois minimum wet vent is 2", it can be rolled lets say a 3" x 2" wye up 45% (should be minimum most places accept 22.5%), head toward the tub then a 2" on it's back with the branch heading up as the vent and the heel catching a tub or shower trap. Max 6 DFU on a 2" wet vent.


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## jnohs

The reason you have to roll up the t on a dry vent is so avoid back flow and a future clogged vent from years of built up up stuff. I have seen this happen many times when running service calls. And rolling the vent above the center clearly fixes this problem. Now the reason that the wet vent/drain has to be on the flat is first we no longer have the back flow build up in the vent because it is a vent and drain and gets cleaned out every time the fixture is used. Thus eliminating a future clogged vent. In addition you also need to run t on the flat on a horizontal wet vent system is because in most situations the vent line is not directly in line with with the drain system. And sometimes needs to be ran 10 south then 6 ft north. Witch means that in order to maintain a wetvent system that can properly vent the waste. The vent/from will need to below the 45 degree angle of rotation and preferably flat to insure maximum piping distance.


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## jnohs

Image 3 that mind lost is what you will run into mostly.


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## Tommy plumber

The Dane said:


> I'd be worried an inspector would fail me if I took a 2'' vent horizontally off the run of a tee servicing a toilet, then picked up a shower and lav with that 2'' vent, even if it is legal. Seems like a neat and convenient way to plumb though too, just looking to see if
> anyone has any experience doing it this way.


how about simply calling your inspector and talk to him about it so you can find out what he will accept and what he will not accept. 




Sent from my iPhone using Tapatalk[/QUOTE]












What you're describing used to be illegal here in Florida. The 3"x2" wye would pick up a W/C, then the 2" would head to pick up a lav {vented line}. In that vented line we would install a 2" wye which then would pick up the tub/shower. This way, when the W/C was flushed, it would not in theory cut off the vent to the tub/shower. The tub/shower was still being vented by the connection of the 2" wye. So the tub/shower drain line was run behind, so to speak, the W/C.

However our code has changed years ago, and I understand that the tub/shower can be directly off the 3" line picking up the W/C.

I still however, will do it the old school way.


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## GAN

One can still create a wet vent using a wye, venting off the branch and rolling it up as long as the upstream fixture is not S-trapped.

No need for explanations, not first rodeo on my end. At least in Illinois (maybe not in the country of Chicago).


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## indyjim

Wet vent. Laid flat, and stays flat for the shower to the right, or else it becomes a s trap. 


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## indyjim

Well, bottom. I apparently suck at taking pics. 


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