bathroom vents

I will be helping my brother plumb up his new bathroom in his addition. This plumbing must pass inspection (Washington State) so I would like to ask a few questions so we have a better chance of getting right the first time. I have been visiting new construction to see how the pros do it and I noticed that they used only one 2 inch vent through the roof for each bathroom. Here is my question.

1) I will be using 3 inch ABS for the toilet drain. How close to the toilet flange does the 2 inch vent need to be connected to the 3 inch pipe?

2) Can this vent connection also be the drain connection for the sink and/or tub?

thanks, steve

A vent ceases to be a vent if it is also used as a drain line. You can combine the vents from the sink and toilet so you only have one penetration through the roof, but you need to combine the drains as drains, not through the vent line. That connection must be nominally at least 42" from the floor, or at least 6" above the rim of the highest fixture (that nominally assumes a 36" kitchen counter with sink plus the 6").

In washington, you can run 6' on a water closet before venting (vent with 2"). You can also tie in your lav to that vertical portion of the vent.

horizontally.

The toilet pipe can run X length in a flat plane (with that minor slope) before the vent comes in.

Here is the general idea: Bring the vent down behind the sink, let the sink connect to it (use a SanTeeat the same level as the P trap tailpiece), and now let that pipe go down under the floor and "wet vent" the tub, by connecting it to the tub drain using a Wye in a flat plane (2x2x1.5or2), then go get the toilet pipe using another Wye (3x3x2). May all your Wye's face the right direction, and may the wind also be at your back.

david

it's been my experience (10 years plumbing in Wash. St.) that wet venting is limited to the vertical. Horizontal wet venting is not allowed. I would vent the tub separatly.

vent

you should be able to use a 3x3x3x2 side inlet tee for the tub, and a 3x2 bushing on top of the tee, or on top of a cleanout tee above the floor depending on the physical requirements of your job, then a 2x1 1/2" tee for the lavatory, and the 2" vent continuing up through the roof. The tub trap would connect directly to the 2" tee inlet, without an auxiliary vent.