Is this wet vent of a toilet OK? Theoretical.

[Jeff H Young]

Thanks for input cool blue plumber and wayne . Ive fallen away from being well versed in code and Horizontal wet venting is something until recently Ive never even concidered or seen in real situations.
I thought Reach 4 drawing was an example of Horizontal wet venting , cool blue plumber saying its not? On normal plumbing before the horizontal came in. I would agree with all the things he said prohibitting this. Everything Ive seen on horizontal wet venting Ive never seen the vent rolled up as he stated. I too thought and still think W/C should be last at end of line but again Im uncertain on this.
Kinda frustrating as everything I see on horizontal wet venting never looks right to me

 

[wwhitney]

I too thought and still think W/C should be last at end of line but again Im uncertain on this.

Yes, under the UPC, that's 908.2.4. But Washington state uses the UPC with 908.2.4 deleted, so with Terry from Washington, it can be a bit unclear at times.

Cheers, Wayne

 

[Sponsor]

 

[Jeff H Young]

Yes, under the UPC, that's 908.2.4. But Washington state uses the UPC with 908.2.4 deleted, so with Terry from Washington, it can be a bit unclear at times.

Cheers, Wayne

Got it ! So it clearly is against UPC. Washington threw that out but that dosent change UPC.
Cool blue had valid point on W/C being last but dosent explain why that issue needs to be corrected before discussion of rolling up vent that didnt seem right to me in horizontal wet vent situation. I guess rolling it up might be permited but I doubt its a requirement

 

[wwhitney]

Not sure I'm following you. Last means downstreamward, the OP's drawing has the toilet last of the two fixtures.

Cheers, Wayne

 

[Jeff H Young]

furthest upstream . would be what I meant.

 

[wwhitney]

OK, so the water closet has to be furthest downstream under the UPC, 908.2.4.

Cheers, Wayne

 

[Jeff H Young]

Thanks Wayne I re read the code and understand. Some of my other posts are incorrect as Ive flip flopped opinions more than once.

 

[Cool Blue Harley]

While not explicit, horizontally wet vented fixtures under UPC 908.2 are clearly exempt from 905.2. With a horizontally wet vented fixture, the invert of the vent connection is the invert of the drainage piping, so it would be impossible to comply to 905.2 and have wet venting. 908.2.1 tells you that the dry vent connection to a horizontal wet vent has to comply to 905.2; the implication is that the wet vent connections do not.

I have found nothing in the UPC that prohibits the configuration in the OP. Nor do I see a performance reason to prohibit it.

Cheers, Wayne

The configuration of the horizontal wet vented WC in the OP is both non-code compliant and substandard in design, thus performance.

Horizontal wet venting is exactly as it sounds. All of the connections are made laterally, on the horizontal. It’s similar to a combination waste and vent system that you might find in a supermarket where there are no interior walls for vents. You are relying on the air space within the system to vent each fixture.

The original question from Reach4 was whether or not the WC combo could be used vertically. No, it cannot.

 

[wwhitney]

The configuration of the horizontal wet vented WC in the OP is both non-code compliant and substandard in design, thus performance.

You haven't provided any code references that support this statement.

I am interested to know if there is a performance issue, can you explain the circumstances in which the OP's diagram would perform differently from a horizontal wye with side branch leading to a closet elbow?

Cheers ,Wayne

 

[Jeff H Young]

The configuration of the horizontal wet vented WC in the OP is both non-code compliant and substandard in design, thus performance.

Horizontal wet venting is exactly as it sounds. All of the connections are made laterally, on the horizontal. It’s similar to a combination waste and vent system that you might find in a supermarket where there are no interior walls for vents. You are relying on the air space within the system to vent each fixture.

The original question from Reach4 was whether or not the WC combo could be used vertically. No, it cannot.

Thanks Cool blue harley I needed the code was 908.2.4 not 905 thats something else but I like your description of the basic mechanics of and comparing to a combination waste and vent. the air space in upper section of pipe. thanks All

 

[Cool Blue Harley]

You haven't provided any code references that support this statement.

I am interested to know if there is a performance issue, can you explain the circumstances in which the OP's diagram would perform differently from a horizontal wye with side branch leading to a closet elbow?

Cheers ,Wayne

The code section I am referencing is UPC 908.2 “HORIZONTAL Wet Venting for Bathroom Groups”

 

[wwhitney]

The code section I am referencing is UPC 908.2 “HORIZONTAL Wet Venting for Bathroom Groups”

Great. I've read that section many times and am familiar with it. Which sentence(s) prohibit the configuration in the OP?

Thanks,
Wayne

 

[Cool Blue Harley]

Great. I've read that section many times and am familiar with it. Which sentence(s) prohibit the configuration in the OP?

Thanks,
Wayne

IAPMO (International Association of Plumbing and Mechanical Officials) is responsible for the compilation and publication of the Uniform Plumbing Code. For a better understanding of of the actual meaning behind each code section, you can visit their website and access the Illustrated Training Manual.

On that website, click the 2018 illustrated code. Read page 297 bottom left of page (908.2). It will explain why each fixture has to tie-in independently and laterally to the horizontal wet vent system. Numerous examples of layout options are included. There are also diagrams explicitly showing the required lateral connections and written explanations. You can email them for clarification. This manual succinctly explains the mechanics behind horizontal wet venting for a bathroom group and the need for horizontal connections.

You are relying on the airspace within the system to vent each fixture. A WC emptying down into a combo, vertically, with a horizontal pipe out the back end, is not vented, lavy or no lavy.

Please post my vote as NO under UPC as requested by Reach4 in the OP. I don’t know how to do it.

 

[Jeff H Young]

That will be ahelp ( IAPMO web site) I will try that out too bad they cant make thier code book a little more clear without a training manual I totaly understand about a w/c dumping down with the vent off that combi never would have been legal on normal venting but on horizontal thought it would be ok then wayne pointed to the 908.2. prohibiting it being vertical. I dont buy that the W/C wont perform as the desighn of a toilet wier is way above the vent take off any way and water closet refills the trap after flush . but do agree that is the code. Thats pretty cool if the IAPMO would actualy answer a question!

 

[wwhitney]

IAPMO (International Association of Plumbing and Mechanical Officials) is responsible for the compilation and publication of the Uniform Plumbing Code. For a better understanding of of the actual meaning behind each code section, you can visit their website and access the Illustrated Training Manual.

Thank you, that is a very helpful resource and does clear up some things for me. However, it doesn't sway me on the topic of the OP:

1) You are correct that on page 297 bottom left the Training Manual uses the phrase "connects independently and laterally to the horizontal wet vent pipe". However, UPC 908.2 does not use that language anywhere within it, or anything like it. That phrase is entirely an elaboration of the Training Manual.

So I would say that if a jurisdiction has adopted the UPC Training Manual into law, then sure, the "independently and laterally" language is in force, and the OP's configuration is disallowed. Otherwise, the UPC Training Manual doesn't get to modify the meaning of the plain language of the UPC itself.

908.2.3 seems the obvious place to include a requirement that connections to the horizontal wet vent be "lateral". The failure to do so there indicates the OP's diagram is allowed.

2) In terms of the performance of the wet vent, how does the orientation of the wye where the toilet fixture drain is connected matter at all? The toilet has to be the downstream-most wet vented fixture under the UPC. That means the wet vent ends at the toilet wye. Upstream of that wye there's going to be adequate air space at the top of the pipe regardless of the toilet wye orientation. Where is the performance advantage?

Yours,
Wayne

 

[Jeff H Young]

Thank you, that is a very helpful resource and does clear up some things for me. However, it doesn't sway me on the topic of the OP:

1) You are correct that on page 297 bottom left the Training Manual uses the phrase "connects independently and laterally to the horizontal wet vent pipe". However, UPC 908.2 does not use that language anywhere within it, or anything like it. That phrase is entirely an elaboration of the Training Manual.

So I would say that if a jurisdiction has adopted the UPC Training Manual into law, then sure, the "independently and laterally" language is in force, and the OP's configuration is disallowed. Otherwise, the UPC Training Manual doesn't get to modify the meaning of the plain language of the UPC itself.

908.2.3 seems the obvious place to include a requirement that connections to the horizontal wet vent be "lateral". The failure to do so there indicates the OP's diagram is allowed.

2) In terms of the performance of the wet vent, how does the orientation of the wye where the toilet fixture drain is connected matter at all? The toilet has to be the downstream-most wet vented fixture under the UPC. That means the wet vent ends at the toilet wye. Upstream of that wye there's going to be adequate air space at the top of the pipe regardless of the toilet wye orientation. Where is the performance advantage?

Yours,
Wayne

I sure dont see the advantage. shouldnt be a discrepency but seems to be one