I plan to move a toilet about 5 feet and a showwer about 3 feet. I have fouynd the main 3" pipe and want to install a "T" for the toliet a:( nd as the new 3" pipe goes through the floor, I want to use another "T" to tap off for the shower. Is this going to work or will there be an issue with odor from the waste going to the main line drain?
Thanks

First off you don't install tees in a horizontal position. Use a Wye or a Combination wye and eighth bend. If you're going to connect the shower to the main you will have to run a separate vent through the roof or revent back in the attic. This vent could be avoided by connecting it to the lavatory drain where it will be wet vented by the lavatory vent. Good luck, Tom