Some do and some don't.
Whatever works there.
I do them dry, but that's me.
when reassembling a union on a gas water heater, is it wise to use a pipe dope or oil on the two mating surfaces of the union.
i am a dope kinda guy, but not on brass unions
the tree of liberty must be refreshed from time to time with the blood of patriots and tyrants
herzlichen gluckwunsch zum dd ich bin uberrascht wen nicht alies da findet
I put it on the faces and the thread for the union nut.
Licensed residential and commercial plumber