Wet Venting

Does anyone know the maximum developed length of a wet vent?

I'm in NY under the IPC. I'm having trouble trying to dry vent my tub as its a clawfoot and so there's no for me to send a vent through. There are walls nearby but not in the path the drain runs to reach the stack (the wall directly behind it is sitting on a double so I cant get a vent up into it). I've been reading up on wet venting but I'm not sure if my fixtures are spaced too far apart to do it. I have attached a layout of my bathroom with a proposed plumbing diagram. The dotted lines are wet vents, the blue dots are vents that will go straight up and the solid red is a regular drain. The shower drain is actually in the middle of the shower more or less where the solid red line starts.

anybody know?

Depends on who's code you are under. At any rate the distances can be found in the chapter on venting. There should be a chart there.

I been doing some more reading and it appears my drawing is not quite right. Only the path of the lav drain is the wet vent and should be the only drain thats dotted. The pipe from the bt and wc to the wet vent are trap arms. So does this mean the distance I need to measure to is from the bt trap weir to the wye that connects to the lav drain? or do I measure to the vertical lav stack? or up to the stack to the dry vent?

If distance is measured to the horizontal wet vent couldn't someone theoretically run the lav drain right next to all the fixtures (until you cant pitch any lower of course) in a bathroom so critical distance is a non issue?

Finally, is there any difference in performance between wet venting and dry venting?

Anyone out there have an opinion on my design?

too many questions, in general.

some of your questions you found answers to, all by yourself.
some of your questions were useless. (E.G. "anybody know?" I'll bet there are hundreds of people viewing this thread who know.)

prepare more before each post.
ask only for the one thing that you cannot figure out by yourself.

to get a clear answer about your drawing, try this:
Redo it with exact distances, post again, remind us that you are IPC in NYC or NY state, and ask one or two clear questions.

E.G.
"trap arm" developed length. Question: distance to measure is from trap to which point?

If you want to be cute, you can ask, "From weir to where?"

The critical distance is from the trap, to the point where it encounters a "vent" which is the point of connection with the lavatory drain. There are MANY ways to install wet vents, which is one reason why we go to school for so long, to learn all of the nuances and possibilities. There is also the issue of hydraulics, such as any negative pressure induced in the tub drain line by the velocity of the lavatory water flowing past its connection.

Thanks guys I will try and be more specific and will post a more detailed picture tomorrow. I live in Westchester county, NY if that helps.

I have two more questions.

Can a wet vent have changes in direction?

I'm planning on doing it like in the drawing most likely with a long sweep if it will fit.

Also I work for a general contractor in NYC and I was on site today and saw the plumbers put in a horizontal vent for a shower. I thought this was a no-no.

Is there an exception in the New York City code that allows this?

I know it will pass inspection because they are an established company and they wouldn't do it if it wasn't legal but I was surprised to see it after everything I've been reading.

The only exception ever regarding a dry horizontal vent is an island vent. That is a different animal. Are you sure the shower isn't wet vented?

Don't know NYC code, but we tend to hear that it is quite ridgid.

let me guess,that horizontal vent,i bet there was a ty before the trap for the shower.that ty then ran horizontal with a little pitch back to the trap,then that horizontal vent turned into a vertical pipe and tied into the rest of the bathroom vents,in the city every fixture gets trapped and vented,i just moved out of the city and am now trying to learn about wet venting and circuit venting,etc.when i plum someones house though i will individually vent every fixture,why does everyone go for mimimum code practices i dont know,its only the industry they are hurting.