I had my rough in inspection yesterday, and everything looked good except my venting for my sinks. I am installing a bathroom lav and a wetbar sink, running into a 2" wet vent that already has a tub/shower on it. Since the distance to the furthest sink is just under 5' from the wet vent I thought I'd simply need to run 2" all the way to its trap arm.

The inspector said that I couldn't have 2 sinks on this setup, however. He's having me run 2" as low as possible in the wall, install a wye, street 45, then san tee at the first sink, continue on with 2" then a 90 and san tee at the 2nd sink. From the top of both san tees run 1 1/2" up then tie back into the 2" wet vent. Once he explained it to me it made sense.

Now for my questions:
- Can I run 1 1/2" out of each san tee for the trap arms, or does 2" need to come out of the wall?

- If the furthest sink was 42" or less, could I have run two sinks on the same pipe? What other ways are there to run two sinks on a single wet vent?

- The plumber installed the wet vent between the W/C and shower. Is this a common practice, or should the vent be installed closer to where the lavs are, especially when they are running 2" under the concrete and can thus be up to 5' away from the tub/shower?

Thanks!

(1)- Can I run 1 1/2" out of each san tee for the trap arms, or does 2" need to come out of the wall?

Yes, you may stub out 1 1/2"

(2)- If the furthest sink was 42" or less, could I have run two sinks on the same pipe?

I would have to know how many fixture units are allowed by your local code to answer that.

(3)-What other ways are there to run two sinks on a single wet vent?

It's very unusual to wet vent lavatories. As a rule we vent the lavatories to the roof and wet vent the tub/shower to the lav drain. Not the other way around. However to answer your question. On his and her lavatories that are set in the same vanity we have a choice between two traps connected through a wye into the stubout or running a continuous waste from one lav to the other and using a single "P" trap.

(4)-- The plumber installed the wet vent between the W/C and shower. Is this a common practice, or should the vent be installed closer to where the lavs are, especially when they are running 2" under the concrete and can thus be up to 5' away from the tub/shower?

Give me more details about this wet vent. Does it drain anything or go to the roof? I don't under stand why it was laid out this way in the first place.
Let me give you a typical rough in. W/C on a 3 or 4" main branch. The 2" drain from the lav tied into the main branch and a roof vent run off the lav. The tub/shower drains into the lavatory drain and is wet vented by it.
So I'm a little confused by your lay out. Regards, Tom

"I would have to know how many fixture units are allowed by your local code to answer that."
Our local code allows four fixture units on 2".

"Let me give you a typical rough in. W/C on a 3 or 4" main branch. The 2" drain from the lav tied into the main branch and a roof vent run off the lav. The tub/shower drains into the lavatory drain and is wet vented by it."

I think that's exactly how it's set up, I erroniously described the sinks as wet vented. I guess since I have a lav on one side and a wetbar sink on the other, the only alternative is the vent setup I described earlier (this is called re-venting?). Using a wye or shared P trap isn't practical since they are not side by side.

Thanks a lot, Tom.

-John