Maximum vent length for new addition

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I am hoping that I can get some advice...

New addition to the first floor; relocating the bathroom and adding a shower. In the end, a bathroom group (5 DFU) and a utility sink (2 DFU) will be vented. I want to route the vent to the attic and tie in up there, but I am not sure that I can.

The drawing shows the resulting drains, existing vents, and proposed vents. Near the main stack, you will see the second floor full bathrooms. I am pretty sure that the toilets both vent directly to the stack, the shower and bathtub use a branch vent, as well as the two lavatories. The current toilet will be relocated, leaving just a utility sink, which I think also vents with the upstairs lavatories. I was hoping to use 1-1/2 pipe to vent the new addition and tie it into the lavatories' vent. From the toilet, it would be 58 feet of vent distance. I believe that is over 42 feet allowed for a 3" waste stack 10 and under DFU. I might be misunderstanding all of this though.

My original plan was to vent using 2" pipe, but you can see from the photo of the stack exiting the attic, I don't have much room to work. The hub that is upsizing the 1-1/2" vents was glued so close to the stack that I don't think I could replace it.

Any advice would be very helpful.

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Sleeping on it; didn't even think about the horizontal run vs vertical run ratio. 58 feet total length with only 22 feet vertical isn't going to work anyways from what I have read in other posts. (1/3 ratio)
 

Reach4

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Sleeping on it; didn't even think about the horizontal run vs vertical run ratio. 58 feet total length with only 22 feet vertical isn't going to work anyways from what I have read in other posts. (1/3 ratio)
I don't know what you are saying here. Two percent (1/4 inch per foot) or more is a good drop. Sometimes 1%.

I did not analyze your nice drawing. https://www.iccsafe.org/wp-content/uploads/20-18927_GR_2021_Plumbing_Venting_Brochure.pdf may be helpful.
 
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I don't know what you are saying here. Two percent (1/4 inch per foot) or more is a good drop. Sometimes 1%.

I did not analyze your nice drawing. https://www.iccsafe.org/wp-content/uploads/20-18927_GR_2021_Plumbing_Venting_Brochure.pdf may be helpful.
Based on the 3" soil stack, I need at least 1-1/2 vent and it can only run 42'. I believe that I need to upsize to 2" so that I can overcome both the distance limitation to the roof vent and the 1/3 maximum vent run being horizontal. Issue is I can't overcome the 1-1/2 to 2" hub in the attic. I am thinking a pipe reamer might let me remove the hub so that I could tie in the 2" vent pipe.
 

Tuttles Revenge

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A pipe reamer would take care of that. Do the work early in the morning while the attic is still cool. And brace off the vertical through the roof as best you can to avoid transmitting movement to the roof boot, especially if its a neoprene boot.
 
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