Pipe tape is an indispensable item for plumbers and others wishing to connect threaded pipe components together and create a leakproof seal. This tape, also known as "Teflon tape," "joint tape," "PTFE tape," "plumber's tape" or just "tape dope," is a thin, flexible membrane that excels at sealing threads. Because the tape is malleable and waterproof, it becomes compressed within the small gaps on the joint threads, effectively sealing them. Learning how to use pipe tape is easy; the trick is to not use too much.
Complete all the needed repairs or installations on the plastic pipes before applying pipe tape. Application of pipe tape is the next-to-the-last step. Applying the tape too early in the repair process increases the chances that it will get dirty, crooked or fall off, resulting in a poor connection after assembly.
Hold the end of the tape against the beginning section of pipe threads, and pull the tape tightly into the threads. Wrap the tape around the threads. The tape must always be wrapped in the same direction as the threads, so look closely before you wrap. Tape may be applied only to the male threaded components, not the female.
Count the number of times you circle the pipe with tape. Limit the wraps to two to three full revolutions of the pipe. For joints that are composed of two different materials, such as copper to plastic, you may increase the maximum number of wraps to five or six. This will allow for more material to be compressed into the wider thread spaces common on nonuniform joints.
Make sure that as you wrap the threaded pipe with tape, some of the tape covers the "end butt" of the pipe. This is the thickness of the walls of the pipe you see when you look at the pipe from the end. By allowing the tape to hang over this "end butt" a little, you reduce the chance that the tape will slide off the threads during tightening.
Tighten the joint in the normal fashion to the desired torque. Take care to not overtighten the joint. If you overtighten the joint and attempt to "back it out" a little, the taped connection will fail.
Hold the end of the tape to the pipe with your thumb when you begin to wrap the pipe with tape.