What is PTFE thread seal tape?
PTFE thread seal tape, often called Teflon tape or plumber’s tape, is a thin white tape made of PTFE (polytetrafluoroethylene, known by the brand name Teflon) that is wrapped around a male thread to make threaded pipe joints leak-tight. The tape fills the gaps between the threads and acts as a lubricant, so the joint can be tightened further.
Application
- Threaded joints in water supply, central heating and compressed air systems.
- Taps, reducers, air vents and filling valves with male threads.
- Gas pipework only with tape that is explicitly approved for gas (stated on the packaging). Work on gas installations must be done by a qualified, registered installer.
How to wrap PTFE tape
- Clean and dry the male thread.
- Hold the fitting with the open end towards you and wrap in the direction of the thread (clockwise for a standard right-hand thread). Wrapped the other way, the tape will unwind as you screw the joint together.
- Start at the first or second thread and wrap tightly, with some overlap, towards the back.
- The number of wraps depends on the tape and the thread; follow the manufacturer’s guidance. The threads should still just be visible.
- Tighten the joint and do not back it off afterwards: turning back can cause a leak.
Common mistakes
- Tape on a compression fitting or gasket joint: there the olive or gasket makes the seal, not the thread. Tape does not belong there and can actually cause leaks.
- Too much tape: the fitting can crack, especially brass or plastic ones.
- Tape over the first thread: loose strands can end up in the pipe or in a valve or tap seat.
Alternatives include hemp with jointing paste, sealing cord (such as PTFE cord on a spool) or liquid thread sealant.
Related terms
- PTFE
- Compression fitting
- Air vent
- Drain cock
- Pressure pipe
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