TAPE
Just do not over do it. Couple wraps, screw em' together. Get carried away with the wrapping---crack.
RLS7201 is correct in saying that manufactures say DO NOT use tape. However, BRUCE the plumber has probably learned the hard way that not doing so frequently results in a leak.
Where Not To Use Teflon Tape:
•Any Gas Connections or threaded connections with a built in rubber seal.
•Flared Fittings
They tend to have a buit in SEAL.
Threaded gas pipe use cement.
Permanent PVC/ABS connections---Glue
Correct me if I am wrong--Bruce.