Where Should You Not Use PTFE Tape? PTFE tape, commonly known as Teflon tape, is widely used in plumbing to prevent leaks in threaded connections. Its versatility makes it a go-to tool for many professionals. However, it's not always the right choice. Misusing PTFE tape can cause leaks, ineffective seals, and even damage to the materials. In this article, we'll explore the specific situations where PTFE tape should be avoided to ensure safety and long-lasting results for your plumbing systems.