Teflon tape is used to seal between almost all threaded plumbing fittings, whether it be copper, brass, plastic or steel pipe thread. About the only exception that I can think of would be brass to brass fittings, and even then, sometimes it is necessary to use teflon tape or pipe dope to seal it.Click to see full answer. People also ask, do you use Teflon tape on an fittings?You should never use teflon tape/paste on AN fittings – the seal is made on the 37* face, not the threads. Pipe threads are a different story – those use tapered threads to make the seal (which isn’t a very good seal BTW), so those damn near require teflon tape/paste to make sure the seal is reliable.Beside above, what can be used instead of Teflon tape? So to start, any PTFE tape is going to be a good substitute for a Teflon tape, because PTFE tape is a non-branded version of the same chemical compound. However, even non-Teflon PTFE tapes can be expensive. Secondly, do I use Teflon tape on brass fittings? teflon tape and firm is sufficent because if you’re just jaming the brass together you can break the seal provided by the teflon or similar, if using unions they seal brass to brass and use the above mention nudge and grunt rule, just be carful not to mishape the fitting as brass can crack or bend with undue force.What is the difference between red and blue Teflon tape?White tape is single density and intended for water pipes of 3/8 of an inch or less. It can sometimes be found in a silver color to match the pipes. Red tape is triple density, for pipes one-half inch to 2 inches in diameter. It is designed for pipes with larger joints, such as water distribution pipes.