Leak from NEW regulators used for roofer torch unit.

First regulator purchased leaked replacement leaked then tape was suggested by the retailer. It's not the bottle fitting as 3 bottles produced the same leak results.
PTFE yes? or No?

My past GPO training was not to use tape or sealant connecting regulator to the bottle, ideas change so what say you 'Gas Safe' experts reading this.

bob, September 2011