Lav vent as trap arm?

[metlc]

I'm replacing a lav sink with a new pedestal lav. The toilet drain runs 12 inches from the 3" closet ell to the main 4" stack. I would like to run a five-foot-long trap arm from the new lav trap, tied into this 12" connection at the stack, which itself is not directly accessible. On one hand, this would seem to be "horizontal wet venting," which is supposedly verboten.

On the other hand, Section 1002.1 of the 2001 California Plumbing Code says: "Each fixture trap shall have a protecting vent so located that the developed length of the trap arm from the trap weir to the inner edge of the vent shall be within the distance given in Table 10-2...."

Table 10-2 lists, for a 2" trap arm, a Trap to Vent Distance of five feet.

So..............? Would that make it OK?

 

[hj]

vent

Usually this would be considered connecting to the "closet bend" which is not permitted. In addition, you still need a vent on the lavatory drain, and you cannot install the "P" trap under the floor.