How to Use Plumber's Tape (PTFE Tape) Correctly

Updated July 2026 · 6 min read · Geelong Emergency Plumbing

PTFE tape — sold as plumber's tape, thread seal tape or Teflon tape in every hardware store — is the lubricant and seal for threaded pipe connections, not the structural fix for a cracked pipe or a misaligned joint. Used correctly it prevents leaks at threaded fittings; used incorrectly it creates them, or worse, provides the confidence to reassemble a connection that the tape can't actually seal. Here's the correct technique, the common mistakes, and when tape isn't the answer.

What PTFE Tape Actually Does

Threaded pipe fittings don't seal by thread engagement alone — the thread cuts into both the male and female component, but the gap between threads is not watertight on its own. PTFE tape fills the thread gap and lubricates the joint during assembly, allowing the fitting to tighten further before binding and creating a seal by compression. It's a thread-seal compound in tape form — soft, deformable, and chemically inert. What it doesn't do: bridge a cracked fitting, seal a joint that isn't fully engaged, or compensate for a damaged thread.

The Correct Wrapping Technique

1. Clean and dry the male thread. PTFE tape applied over moisture, oil or debris doesn't bond to the thread properly and can slip during assembly.
2. Wrap clockwise, looking at the thread end. This is the direction the fitting tightens — wrapping with the tightening direction ensures the tape seats more firmly as you tighten rather than unwrapping and bunching. This is the most critical detail. Wrapping anticlockwise means the tape strips off as the fitting goes on.
3. Start at the second thread from the end. Tape on the first thread gets cut and displaced as the fitting engages — starting from the second keeps the seal in the compressed zone.
4. Overlap each wrap by half the tape width. Single-width wraps leave gaps; more than 50% overlap wastes tape and can create too much bulk.
5. Two to four wraps for standard water supply fittings (1/2" and 3/4" BSP threads). Gas fittings typically call for more wraps and may require additional thread compound per AS/NZS 5601 — follow the gas fitting specifications for any gas connection.
6. Pull the tape tight as you wrap so it conforms to the thread profile rather than sitting loose.

How Many Layers?

The feel test: after wrapping, run a fingernail across the tape-covered thread — the thread profile should still be visible through the tape, not buried under a thick mound. Two to three visible thread peaks under the tape is the target. Fewer wraps = inadequate seal; more wraps = binding before full engagement, which prevents the fitting tightening to the correct depth.

When PTFE Tape Is Not Enough

Compression fittings (the kind under most kitchen and bathroom sinks — where the nut tightens a ferrule onto the pipe) don't use PTFE tape. These seal by metal-to-metal compression, and tape in the wrong place creates bulk that prevents the ferrule seating correctly.

Push-fit fittings (Speedfit, SharkBite etc) use internal O-rings — tape on the pipe makes it harder to insert and doesn't improve the seal.

Cracked fittings or damaged threads: tape cannot bridge structural damage. A cracked fitting leaks through the crack regardless of how much tape surrounds the thread, and a thread so worn it can't engage properly won't seal with tape alone. Replace the fitting.

Gas fittings in many situations: Australian gas standards (AS/NZS 5601) specify approved jointing compounds for gas, and PTFE tape alone may not meet the requirement depending on the fitting type. Licensed gasfitters use AS-approved materials — don't substitute tape for gas compound on gas fittings.

PTFE Tape vs Pipe Thread Compound

Thread compound (also called pipe dope or jointing compound) works similarly to PTFE tape but in paste form — it fills thread gaps and lubricates assembly. Some plumbers prefer compound for large-diameter threads and irregular thread forms where tape doesn't conform well. The two can be combined (tape first, thin layer of compound over it) for maximum confidence on critical connections. For household DIY on standard BSP water fittings, tape alone is appropriate.

One last practical note for the common scenario where tape has been applied but the joint still leaks: disassemble completely, remove all existing tape, dry and inspect the threads for damage, and start fresh with the correct clockwise-wrap technique. Re-taping over existing tape nearly always fails — the old tape is compressed, the thread profile is hidden, and the new wrap does not engage correctly. The instinct to add more tape is the most common PTFE mistake, producing a leaking joint covered in too much tape rather than a sealed joint covered in the right amount.

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Related guides: How to fix a leaking tap · DIY plumbing in Victoria · How much does a plumber cost