Check this Venting...

Take a look at the existing setup in the diagram. What I need your help with is if the tub needs to be vented separately from the lav. I've thoroughly confused myself trying to separate the difference between wet venting and combination venting and so on... Any help appreciated. There are no fixtures above the tub/lav. drain on the vertical stack.

vent

Looks good. The tub is connected at, or above, the toilet connection, and the lav seems to be properly vented. As long as there is not another bathroom above this one on the same drain line.

Vent

Thanks. Another question. I don't have enough vertical room to fit in 2 separate san. Tees to serve the toilet and the shower/lav. Can I use a double sanitary T to serve the WC with a side inlet on the same T for the tub/lav?