Vent question below flood rim. When is "horizontal" horizontal?

[OJB]

I am confused by the following:

- On one hand code (IPC) clearly states that " 905.4 Vertical rise of vent. Every dry vent shall rise vertically to a point not less than 6 inches (152 mm) above the flood level rim of the highest trap or trapped fixture being vented. " It even has the following diagrams showing acceptable vs unacceptable:

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I am also well aware of many posts here and elsewhere pretty much saying "No flat vent below flood rim, period" ... sloped or not, etc ...

Yet below is a diagram with the vent line connecting to drain line with a wye angled at 45 (ok, that's vertical, not horizontal per code) followed by a section sloped at 1/4in per foot (clearly << 45 deg, so not vertical?), and clearly under the flood rim of the toilet.

With the following comment: "When a branch drain must travel through a floor platform before reaching a stack, the drain must slope gradually. Here, the angle the vent takes off from the toilet drain is critical—it must not be less than 45°, as depicted in the cross-section drawing on the facing page."

So my question is: Is that diagram a fail code wise? ( I've also seen other similar diagrams from other sources claiming that's ok.) Or is the 45 deg orientation of the wye from horizontal, which would end up higher than the top of the drain pipe, enough? And if this is code, is there a limitation in length (as long as you can maintain the 1/4in /foot slope) between the two 90 deg elbows?

Confused ... thank you in advance for any comments.

 

[Reach4]

1. Anything with 45 degrees of plumb is considered vertical for this dry venting purpose.

2. Wet vents can be horizontal.

Your bottom picture would not be an acceptable dry vent today.

https://wabo.memberclicks.net/assets/pdfs/Plumbing_Venting_Brochure_2018.pdf has some nice IPC venting info, including a big superset wet vent drawing on page 12.

 

[Sponsor]

 

[OJB]

Thank you for your response! Would you consider it "borderline", as in not code but would work in most situations? Or alternatively could it be one of those "some inspectors or juridiction would fail it, others would pass it" kind of thing?

The diagram is from "fine homebuilding," exerpt from "Renovation, 5th Edition (The Taunton Press, 2019) by Michael Litchfield and Chip Harley"

Here's another diagram from a different source, home and garden, granted not exactly the authority on the subject

 

[wwhitney]

So my question is: Is that diagram a fail code wise?

Yes, for a dry vent. It and similar illustrations reflect outdated installation practices that do not meet code.

Cheers, Wayne

 

[Jeff H Young]

yep illegal in ipc legal in upc if structural conditions require and inspector approoves the thing about strucural conditions requiring is that the inspector can say often that no you just chose a crappy way to plumb it and for example a horizontal wet vent might have solved the issue.
I plumbed many many toilets as the one in illustration on post number 3 but I was taught that way only years later to learn that it isnt an automatic aprooval.
BTW a flat vent is kinda slang term but if its less than 45 degrees any portion below that "6 inches above flood level " thats what is no good

 

[OJB]

Understood, thanks. I actually do have structural limitations (like double i-joists in the wrong place the top of which I can't touch) but I am going to play it safe ... I don't like boxes behind a toilet to hide a few inches of 2" vent pipe but that's what it's going to have to be ...