Kitchen Island Sink Vent

[DYIWannabe]

Instead of the typical loop vent for an island which would require concrete work, I'm opting for a column on the island to run the vent up to the attic to tie-in to a near by vent. Considered the AAV, but decided to avoid that path if possible. Would either of these vent configurations work and be code compliant? Neither configuration have the vent above the sink flood rim or 42" until the vertical run up the column.

 

[Terry]

Unless you are at 42" high on the vent, those won't pass. Vertical is 45 degrees. You trap arm can be 60" on 2" though.

I'm also seeing them done this way now in some places.
This one was in Everett Washington.

I should take a picture of how they finished this out. It's my son Jamie's new home he bought.

And this is what I have done in the past.

 

[Sponsor]

 

[DYIWannabe]

Terry, Thanks for the quick response. It sounds like it has to be either the loop or the AAV or raise the horizontal vent to meet the code requirement. I'll look to redesign. Now as an intellectual exercise, purely from a functional point of view, why is long trap arm (42" for 1 1/2" and 60" for 2") better than horizontal dry vent? Wouldn't the long trap arm be more likely to plug requiring more frequent clean out. The horizontal vent would only fail and require cleanout after an overflow event?

Also wouldn't my two options perform better than the loop vent and the AAV?

Normal condition: sink does not overflow
Option 1: No issues
Option 2: No issues
42" height horizontal vent: No issues
Loop Vent: No issues
AAV: could fail over time as it has moving parts and seals, etc.

sink backs up and overflows:
Option 1: liquid backs up to the horizontal section, possible accumulation of solids, potential plugging and loss of vent function, require snaking of the vent to mitigate.
Option 2: liquid backs up to the horizontal section, possible accumulation of solids, potential plugging and loss of vent function, might be better than Option 1 since the slope is bigger, require snaking of the vent to mitigate
42" height horizontal vent: No issues as the sink will overflow and no liquid will travel to the horizontal section
Loop Vent: if drain stop is further downstream of the loop then the liquid will fill the vent line including the horizontal sections, possible accumulation of solids and potential plugging and loss of vent. require snaking through cleanout. As the horizontal vent line is lower with minimal slope, accumulation could be worse than Options 1 & 2?
AAV: more opportunity for failure if valve does not properly seat.

 

[Terry]

And you think plumbers haven't had to deal with venting below the flood level before?

I would much rather have a five foot trap arm that I can snake, than a vent that doesn't have that option.
Lav, 42"
Shower or sink on 2", 60"
Toilet, 72"

 

[DYIWannabe]

Fair enough. Thanks for the pointers. Now, the design has no more horizontal vents below the flood rim. Instead there is a long trap arm and long waste line with some horizontal turns. I also included a couple of cleanouts. Could this work?

 

[Terry]

If it's my home, I'm going with the AAV. That's a lot of extra piping there.

The 7/8" could have been angled better here. It's a gravity down from the air gap.

New construction above.

In a rental I stayed at.

 

[DYIWannabe]

Terry, thanks for sharing those pictures. If I go with the AAV option, this is what I think it will look like. It's a lot of simpler.

 

[hj]

I have done option #2 many, many times (sometimes using 60 degree bends to lower the angle), and it has ALWAYS passed inspection. In fact #1 has been approved also as long as it is as high as possible under the window.

 

[DYIWannabe]

Thank you HJ for the comments.