[premisis one]

I am adding a powder room c/w toilet and basin. I was told that if I use 2" piping all the way up to the basin tail piece that this would act as a vent if tied into the toilet drain. Will this work properly?The toilet is on the main floor and it will be about 10 feeet away from a main sanitary drain. Thank-you:confused:

[speedball1]

I am adding a powder room c/w toilet and basin. I was told that if I use 2" piping all the way up to the basin tail piece that this would act as a vent if tied into the toilet drain. Will this work properly?The toilet is on the main floor and it will be about 10 feeet away from a main sanitary drain. Thank-you:confused:

Nice try but no cigar! Don't hire the person that gave you this advice to do the job.
You would be in violation two ways if you attempted this. One, you would be building a "S" trap by using a elbo to pick up the trap instead of a tee with a vent out of the top, and two you would be discharging a major fixture,(your toilet) past a unvented minor one.
However there is a way around running a vent out the roof, if local codes permit. You may connect the lavatory drain to the toilets drain line if you place a AAV cheater vent, (see image) on the tee instead of running a vent.
If this is a first floor installation you may use 3" for the toilet and 2" for the lavatory drain. Good luck. Tom