Venting questions

Hello,

I am new to this forum and have been searching for days now for an answer to my problem online. Short of having a plumber come out to just give me the answer I need I thought I would try this. I understand the concepts of plumbing as far as p-traps and such but I am totally confused on the concept of venting, atleast in my situation. I do not currently have any pictures because i just started ripping out the drywall and noticed that my first floor powder room and laundry room does not have a vent from each fixture (i.e.--toilet, sink, and washing machine). These items are sitting on concrete slab. Now I know that the main stack is vented which sits in the wall behind the sink and toilet on the first floor and runs straight up behind the bathroom on the second floor.

Here's my problem. I am going to relocate the drain for the washing machine and am quite unsure how to add a vent. There is no easy way to tie into the existing vent on top of the stack from the side of the house I am working from due to a lower roof. Can I add a second vent through the lower roof and tie the first floor sink and washing machine to this in the lower roof attic or will this cause flow problems due to the main stack being vented? I live in a city where the UPC is law.

You can have as many vents as needed.
Or you can tie vents together above the flood level of the fixtures and go up with one vent.
So much depends on the existing framing and layout.

Helpful Plumbing Hints for Residential Construction by Bert Polk Plumbing Inspector Lincoln County

But it is ok to have the second vent lower than the first on seperate roofs, even if it is lower than the second floor toilet? O, and thanks for the quick reply!!

The lower floor vents can daylight separately. That means yes, on the roof for the first floor. The vent needs to be 10 feet away from an opening window horizontally for dispersal.

"If" the lower floor vents are tied into the second floor vent, then it needs to be six inches above the second floor flood level.

From what I can tell everything is wet vented to the main stack. I just want to seperate the first floor powder room and the laundry room to a dry vent out of the first floor roof (these will still be wet vented to the main stack with the second floor bathroom).

A wet vent section is only for one floor. A wet section from the second story can't vent a lower floor.

Thanks for all of your help...I guess I am still slightly confused here...Since everything currently is using the top of the main stack as its vent off the second floor roof (everything including first floor powder room, second floor bathroom, and first floor laundry, and kitchen sink), I can still vent the powder room and laundry room together out of the first floor roof without making any other changes?

Generally, once a pipe becomes a drain, it is no longer a candidate to be a vent. That's why you need to go above the flood rim of anything above you to get above the point where it became a drain verses a vent. Now, will it work, sometimes, and it also depends on the size of the pipe, but then you get into cutting hairs, and special circumstances that may not be met in most situations.

In your situation, FORGET about the existing pipe and vents. All you have to worry about is your new one, and it has absolutely NOTHING to do with the existing venting.

Thanks for all the replies...