Half Bath Venting

[bdaalex]

Hi,

Plumbing in a half bathroom as shown in the photo below. Basically a sink drains vertically via 2", bushing up to 3", continues downstream to the toilet wye, continues to a 3x2x3 san tee for venting and then steps up to a 4" sewer pipe via a bushing. My question is, does the sink need its own vent (in orange) when the distance from downstream vent is 8'?

The complication is that there are two 1/16 bends in between sink and vent so that the total drop is definitely more than a pipe width. I imagine there are two answers to my questions, code and practice. This is a half bath sink without a stopper so realistically I cannot imaging the trap weir ever siphoning off, but I can also see code requiring the vent.

thanks

 

[hj]

That 'downstream vent" is just about useless and does absolutely nothing as far as venting the sink is concerned, so YES, it does need its own vent, and in most cases you can also eliminate the other vent, or leave it. In some areas the 3" line to the sink would not be allowed.

 

[Sponsor]

 

[bdaalex]

thanks for the reply. two follow ups:

-I havent punched through my roof yet so how could I eliminate the vent downstream of the toilet?
-why would the 3" to the sink be bad?

 

[Terry]

The vent on the lav is required.
The vent to the left does nothing for the lav.
Better off using a 3x2 wye to pick up the lav, and using an end of line 90 for the toilet.
I have gone 3" to the lav and installed a cleanout there below the lav.

 

[bdaalex]

I was trenching solid concrete and wanted to avoid digging anything but a straight line in the floor, hence no end of line 90 for the toilet. I do know that was better.

Much to my surprise, inspector signed off on this with no vent by the sink at all, our code allows 10' horizontal between vents in 3" pipe and 8' for 2". That is why I used 3" between toilet and sink even though not needed. I did not think there was anything bad about it though.

Despite approval, I might do the below just to be safe. It's not much cost or work to run 2" over the drop ceiling, I just dont want to punch the roof twice.

 

[Terry]

When I travel outside the US, I see horrible plumbing. Your inspector passing it off doesn't mean it's working for you. It just means he doesn't understand why we have codes and what they intend to fix.

 

[DIYWorker]

I have a quick question to this thread. I have a 1/2 bath that is in the opposite setup. The Toilet is first and the sink is second. They are both less than 6 from the main 3in line and feed directly into it. Neither have a vent pipe attached. Is this still a problem in the opposite direction. I am asking because we have been getting some urine smells from the bathroom when we first moved in and it comes back occasionally. I recently found that the toilet seat was not bolted down. (Why is perplexing? unless it was a trick to get us to move in) So I am not sure if it was due to the toilet seat or improper venting. Thank you in advance!