drain/waste vent question

Hi,

Thanks in advance for the help. I'm wanting to add a new lavatory to my bathroom upstairs. I hope i can explain my situation well enough in words.

The existing toilet drain is about 4 feet from it's 3 inch waste vent. The new lavatory I want to add is about 6-8 inches away from the vertical section of the 3 inch waste vent for the toilet. Is it okay just to add a sanitary Tee into the waste vent and add my new lavatory drain there? Will creating this wet vent be an issue?

Or, is it a better idea to run a separate vent line off of the new lavatory and then tie into the waste vent higher and run a separate drain for the lavatory and tie in with a Wye connector near the toilet drain.

I just spent a ton of time researching toilet venting. Seems there is just as much support for a vent as there is for no vent. (A real hotly debated issue) I elected to wet vent the drain via a lav wye 7 feet from the flange. The toilet plumbing I removed for this remodel had no vent at all and the 3" drain line ran 11 feet. I worked fine for many years. I did not know it but toilets are considered self venting but codes require them on systems to protect other trap seals. (I'm an a DIY'er so take my comments w/ caution.. Good luck. Great site here for info...

There is no issue with your lav drain being connected. The lav will still need it's own vent.