Horizontal Wet Venting

[James Henry]

I have some questions that have been bothering me for a while now. Their are hundreds of web pages from different authors and from different times dating decades back that claim ' The toilet must be the last fixture on the HORIZONTAL drain entering a HORIZONTAL wet vent system". I have a manual written by a man who writes the Colorado state plumbing license exam and collaborated with a man that worked with the ICC, and in that manual he never mentions that the toilet has to be the last fixture on a HORIZONTAL wet vent system, And, I cannot find it in the UPC or the IPC, and I've searched many. he also included diagrams and a few of them showed the toilet being tied in before the shower or bath tub. However, on a VERTICAL wet system, both the UPC and the IPC throughout the decades state as your well aware that you can't have a Major over a Minor.
QUOTE: "ON A VERTICAL WET VENT THE WATER CLOSET SHALL BE THE LOWEST FIXTURE ON THE SYSTEM". So i'm wondering if this is not getting misconstrued or has someone had a plumbing inspector in their jurisdiction who required them to have the toilet last on the line. I just want to mention one last thing. When water runs down a HORIZONTAL pipe, the water flows in the bottom half of the pipe and the air flows in the top half of the pipe. When the water flows down a VERTICAL pipe, the water tends to swirl around the inside of the pipe, hence, the shower trap siphoning. I wish we all had one universal plumbing code, but it is what it is.
I welcome any comments, or jabs, if you need to. that's why I'm asking.

 

[wwhitney]

I cannot find it in the UPC or the IPC, and I've searched many.

Just checked the 2016 California Plumbing Code, based on the 2015 UPC. 908.2.4 (marked as new or modified from the previous version) says: "The water closet fixture drain or trap arm connection to the wet vent shall be downstream of fixture drain or trap arm connections to the horizontal wet vent."

Cheers, Wayne

 

[Sponsor]

 

[James Henry]

Yea It turns out UPC / IAPMO does in fact require it. I'm still researching the IPC / ICC. If you find a document from the IPC / ICC. Let me know.

 

[Tuttles Revenge]

When horizontal venting was introduced in our area '06-'07ish, we could install back to back bathrooms but had to have the toilets most downstream.

Our local version of the UPC amended that WC as most downstream fixture out. Its based on the ill conceived notion that you need other fixtures upstream of the toilet to wash down stuff left behind by the toilet. That was explained to me by an inspector once when I installed a horizontal wet vent system in a powder room.. which is Not a Bathroom group (even tho his boss had a drawing online showing H-Venting in a powder room configuration) .. Was all I could do to not call him out on it.

Use Alternate Procedures and install it like we do.

https://www.kingcounty.gov/depts/he...ocuments/plumbing/horizontal-wet-venting.ashx
908.2.4 Water Closet. The water closet fixture drain or trap arm connection to the wet vent shall be downstream of fixture drain or trap arm connections to the horizontal wet vent. This section has been deleted by Washington State amendment, hence the strikeout of this section shown. Therefore, the water closet can be connected at any point within the wetvented horizontal branch drain. However, it cannot be located upstream of the dry vent serving the wet-vented horizontal branch drain as outline in Section 908.2.1.

Towers downtown seattle are using some seriously messed up venting systems, based on alternate methods.

 

[James Henry]

When horizontal venting was introduced in our area '06-'07ish, we could install back to back bathrooms but had to have the toilets most downstream.

Our local version of the UPC amended that WC as most downstream fixture out. Its based on the ill conceived notion that you need other fixtures upstream of the toilet to wash down stuff left behind by the toilet. That was explained to me by an inspector once when I installed a horizontal wet vent system in a powder room.. which is Not a Bathroom group (even tho his boss had a drawing online showing H-Venting in a powder room configuration) .. Was all I could do to not call him out on it.

Use Alternate Procedures and install it like we do.

https://www.kingcounty.gov/depts/he...ocuments/plumbing/horizontal-wet-venting.ashx
908.2.4 Water Closet. The water closet fixture drain or trap arm connection to the wet vent shall be downstream of fixture drain or trap arm connections to the horizontal wet vent. This section has been deleted by Washington State amendment, hence the strikeout of this section shown. Therefore, the water closet can be connected at any point within the wetvented horizontal branch drain. However, it cannot be located upstream of the dry vent serving the wet-vented horizontal branch drain as outline in Section 908.2.1.

Towers downtown seattle are using some seriously messed up venting systems, based on alternate methods.

When I went through my apprenticeship I was under the UPC and had to learn that. Now that I moved I'm under the IPC and I'm trying to understand every aspect of it. I found out that the IPC is proud of saving money under their code rules. If they'll past the test of time, we'll see.

 

[James Henry]

https://www.iccsafe.org/forum/intl-plumbing-mechl-fuel-gas-codes/horizontal-wet-vent/

For what it's worth.

 

[Tuttles Revenge]

The more and more I look at varying codes and procedures, I get the sense that the UPC relies more on the tradition of "that's how we've always done it" rather than solid engineering and testing.

 

[Reach4]

The more and more I look at varying codes and procedures, I get the sense that the UPC relies more on the tradition of "that's how we've always done it" rather than solid engineering and testing.

United Plumbing Cartel?