"New" bathroom vent help.

[jaleadeuva]

Hello,
We had to remove our bathroom for major structural renovations, all that is left is our 3in roof vent in the attic and the stubs of our waste vents on the basement floor. (1x 3in + 1x 2in abs pipe connected to main line to septic).

Our old bathroom group only had venting on the toilet which connected below the floor and headed off horizontally untill it could make it up through a void in a closet. The other two fixtures connected to the main waste line on their own non vented run.

My questions would be:

can a vent run horizontally like it did below the flood level rim of its fixture (toilet)?


If it is only serving one fixture could it be 2inch in diameter whilst going through the walls and then increase to 3 in the attic for the roof penetration?

 

[wwhitney]

(1) Not for dry vents, which is what you have (assuming that the red cross-hatched pipe receives no drainage). For wet vents, yes.

(2) Yes, unless your plumbing code has a requirement for a "main vent" or the like that is full size from the building drain (drain that exits the building) to the roof, and you have no other full size vent that could be the main vent. I'm not sufficiently familiar with the Canadian code to know if that is required, so you'll have to check.

But what about venting the lav and the shower ortub? If you dry vent one of those, then it can wet vent the WC. For example, if the drain of the lav in the room with the WC connected to the vertical red cross-hatched pipe in your diagram, the part of the vent that the lav drains through would become a wet vent, and then the horizontal section under the floor would be OK.

Cheers, Wayne

 

[Sponsor]

 

[jaleadeuva]

Thanks,

I'm new to this and pretty early in the process.
i've been trying to get my answers from the code book but it's a pretty brain melting read.

Is it seen as good form to vent a three piece bathroom group on 1 dry vent (the other fixtures being properly wet vented)? Or would it be preferable to dry vent the most fixtures possible individually?