My husband and I recently replaced our wood burning stove. We replaced it with a larger used stove. My question is regarding the piping. Our pipe goes out through the roof. Where the pieces join, do we need any type of sealer or is it ok just to screw the pieces together? Our new/used stove heats tremendously better than our old one, but are there any other things I should be on the lookout for (i.e. potential problems). We took a chance buying a used one and installing it ourselves.

The piping on any natural draft appliance does not need to be sealed. You want to use 30 ga. vent pipe and also make sure that the piping that goes through the roof is double wall pipe, and that it has a minimum of a 1" clearance from bombustable materials.
Off the stove, install a tee with a cap on the bottom for cleanout then install each piece after the tee so the next pipe fits over the one just installed. "the pipe going up should fit inside the next higher piece".... A crimping tool may be needed....

Good luck..E mail welcome