Waste Vent Piping

[GS-Louie]

I am plumbing the bathroom in the new garage. I will have a toilet and one sink. Can I use 1 1/2" DWV piping?

I plan to go up the wall, over the headers and then down, venting through the soffit. Is that acceptable or must I go out the roof? The outlet would be about 11 - 12' above the ground. and the building is free standing.

Thanks,

Lou

 

[Cyberbear]

"I plan to go up the wall, over the headers and then down, venting through the soffit."

I'm not sure I understand your plan, especially the "...and then down, ..." part. I've done what you describe but every portion of the DWV always went up towards the roof and out.
The main thing is to not create an area that will trap gas or liquid.

 

[Jackfre]

No, you need a 2" vent for a WC. I know it is done but I would never vent under a soffit. You are talking saturated, bacteria carrying air. At the least you will end up with a smell as the breeze carries and you may grow some crud under the eve.

 

[usa#1]

Look up air admittance valve. I think it will save you some work if it's code approved for WC. I reread your post, I missed the "new" part. I believe you have to have at least one main vent stack so the admittance valve most likely not meet code requirements in this case.


You'll have to check plumbing code for vent/drain sizing. One of the folks on GJ board more familiar with the plumbing code will most likely spell out what will work for you.

 

[TheEquineFencer]

I think you mean, you do not want to knock a hole in the roof? You want to vent out under the eve?

 

[kbs2244]

In short, no, you cannot do it that way.
You need 2 inch with as straight up as possible and through the roof.
If you are in a freezing area your through the roof will have to increase to 4 inch so it will not freeze over.

If the walls are open, have a plumber do it.
You are talking half a days work and he will have the code memorized and the roof seals in the truck.

 

[Rosco]

My garage 1/2 bath has a 2 inch vent for the toilet and sink run into the attic and is topped with an air admittance valve. Inspector and code approved for my county in Ga.

 

[zmaxmotorsports]

What plumbing code are you under? Id run it up in 2" from the stool then tie the 1 1/2" from sink into it somewhere above flood level of sink.
Take it up to about 16" below the roof in 2" ,then install a 2x4 increaser and continue it 12" above roofline in the 4"

 

[TheEquineFencer]

Mine passed AHJ approval. It makes it out from under the eve and above the roof.

 

[Scott r c]

It doesn't need to be 2", although code in your area may or may not say so. Generally the vent is 1/2 the diameter of the drain.

 

[GS-Louie]

Thanks for all the help so far. I was hoping to be able to vent through the soffit to avoid going through the roof.

The drain is 3". The WC is at the end of the line. about 16" along the line is the tee for the sink in another room that comes up through the floor. The line then continues out about 22' and goes in to the septic tank. It is a small system only for the garage.

Based upon recommendations above, This is how I see it.

From the 3" stub, 90 elbow, short piece of pipe, reducing tee to 2". One 2" goes up for the sink drain, the other side goes goes to the wall and turns up to the roof. The guy who installed the septic was going to install a 2" vent from the waste line up the outside wall but I didn't want it there. Our house has a 3" and a 2" waste vent.

I would just call a plumber but that is easier said than done in the area where I live. They may or may not call back, probably not. They may or may not show up as promised, and the job may or may not do the job correctly. So, I do things myself

Again, thanks for all the help and advice.