The correct answer is to use pipe dope the Teflon tape over the pipe dope. Teflon tape is not a sealant of any sort is only a thread lubricant. A true pipe thread sealer is pipe dope. As I just asked a sprinkler fitter why he was pipe doping then Teflon taping all pipe threads and...
Pipe dope is a chemical sealant with a texture similar to a thick paste. It is made to stand up against the types of fluids it contacts. It can be purchased at any hardware store and comes in cans of various sizes with applicator brushes or can be bought in a tube. It is advertised ...