So I am about to get into a plumbing repair which seems that I may be able to handle. The job is the replacement of a copper, domestic hot water coil which is inserted into my boiler (a prehistoric, on demand hot water system). I can do the standard 1/2 in copper fitting work, but my question is where the threaded copper nipple attaches to the threaded copper flange. For this connection I'm unsure if I should use Teflon tape or pipe dope, or something else. TIA