Double Lav drain question

My first post in this excellent forum! Lots of very helpful people in here.

I've read some of the other single to double lav conversion threads and I have a question. I'm working on a friends condo and unfortunately I was not able to get a photo of the rough plumbing to post, so attached is a rather terrible drawing made with good old Microsoft paint. Originally there was a single sink feeding that long 10' run to the drain and vent. Now the plan is to convert it to a double lav and rough in all the plumbing inside the wall.

Basically, I am wondering if the following drain set up shown with the black lines meets UPC in terms of venting. If not, would adding a secondary vent as drawn with the red lines solve the requirements? Also, is it an issue that the primary drain that both lavs would now feed is only 1 1/2" and not 2"? The distance between the stubouts is approximately 50" and obviously each sink will have it's own P-Trap. Any help that can be provided is appreciated. Thanks!

WITHOUT the red line, there is NO venting, so it IS necessary, as is the PROPER fitting at the juncture of the two drains. NO sanitary cross, or "double sanitary tee" if that is what you want to call it, and NO double "Y"/combo either.

HJ. Thanks for the reply and the confirmation. I will add the vent. I must admit, I was planning on using a 1 1/2" double sanitary tee to attach everything (like this http://www.pexuniverse.com/store/product/1-12-pvc-double-sanitary-tee). If this is not acceptable, then is there a similar type fitting that would be acceptable? Do I need to use the "back-to-back" double fixture type? It seems like that type of fitting is used in this image which is found in similar thread discussing this topic (shown here: https://terrylove.com/forums/showthread.php?22539-Double-fixture-tee-or-double-sanitary-tee). Thanks again!

Okay. I plan to use the Double fixture tee. Thansk for the confirmation HJ. Two more questions:

1) Is it acceptable to use a reducer on the fixture and drain it in to a 1 1/2" line?

2) Is an AAV acceptable in place of running vent line up and over to the existing vent.


Performing the full vent is going to be a rather large job and tear up. Bottom line is that I will only do this in a safe and solid manner, but if an AAV is acceptable and will function properly, then this would be the much preferred method.

>>>1) Is it acceptable to use a reducer on the fixture and drain it in to a 1 1/2" line?<<<

I don't understand what this means, if you are running a dual lavatory the drains should be 1-1/4 or rarely 1-1/2 why do you need a reducer?

UPC does not like AAV's, I don't like them even if they are allowed; you are adding a mechanical device to a line which can go bad when you use mother nature's vent you RARELY have problems