I was looking at a picture showing a wet vent for lavatory and the tub(both)... Is both OK? And is tub at least for venting purposes same as a shower unit? The vent comes down between the toilet and tub picking the lav drain first then proceeds to 2" line from tub to toilet then out.
How far back from elbow for the toilet would I put my "y" for lav and tub, any requirements here?
Lastly, is there any bad news about wet venting, seems common practice I see, but is the only thing bad about it is that it is tricky or is traditional venting to all fixtures the better deal?
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Hey Sparky... off to work now, but if knowone answered when I get back I will then. Good day.

Hi Sparky:

Your picture is good, but not very accurate in terms of which fittings to use. I will explain.

Wet venting is all about distances from trap to vent connection and sizes of piping.

Let's use your pic. And work out from there. We will assume a 3" waste line for bathroom toilet.

In this case, toilet can be wet vented by the lavatory AS LONG AS VENT FITTING (3x2 wye here) CONNECTS INTO TOILET DRAIN ABOVE CENTERLINE OF DRAIN AND CONNECTS WITHIN 8 FEET OF TOILET ELBOW AND IS 2" PIPE to the lavatory (branch off 1.5" pipe to lavatory sink trap) and then continues 2" ALL THE WAY OUT THE ROOF (OR TERMINATION POINT THAT IS 2" or larger vent such as the vertical 3" vent stack in the pic....note here that that vent connects into the vent stack at least six inches higher than the top of the sink...that is critical...ok?)).

NOW, we also want to wet vent that tub...well in your picture they show the lavatory coming off the horizontal 2" pipe (USE wye fittings when coming off horizontal drain line). If this fitting to the lavatory is within 6 feet of the tub ptrap then it can also serve as a wet vent for the tub.

I have used numbers (distance trap to vent) from the uniform plumbing... your area may use a different code (check with local inspector)... but the principles are basically the same across the country... basically.

I have also super simplified this for you... could not include ALL the details of wet venting in 2 paragraphs.

If you want more info. Make a drawing (I used my paint program before and then converted to format using site program) with critical distances and post to this site (under go advanced). We can tell you more then.

And wet venting is fine compared to individual vents as long as critical distances are maintained... Fixtures are very much individually vented in a way... huh?

Anyway, that's it. Get back to me.