second sink vent

[kingnus]

I have a master bath with a 78 inch long vanity and just one sink located at the right end of the vanity. The 2.0 waste line runs to the left inside the wall to a 4.0 dia pvc pipe about 85 inches away that goes to the basment to the septic and runs straight up thru the roof as a vent. I believe it vents the sink and toilet. I would like to tie in between the present sink and the 4.0 pvc for the second sink. Will I need a new vent pipe between the two sinks or will the one 4.0 vent pipe be ok?

[hj]

Under our code you would have needed an auxiliary vent as soon as the pipe was 48" from the sink, much less 80"

[construct30]

Under the 2006 IPC a two inch pipe can run, with proper minimum slope, eight feet off a main vent stack. It must not have any rises in the pipe and must come off a T not a Y, but I believe it can only work, be code compliant, with a single fixture, so in your case, if I followed you correctly, it might be OK now if the sink is the only thing on that pipe, it is sized at 2" one size up as required, add a sink and no.

Section 906.1 and 906.2

[kingnus]

Thanks to all for your replies.
Kingnus