PTFE Thread Seal Tape

What the tape actually does inside a threaded joint

PTFE thread seal tape — still called Teflon tape by most fitters — does two jobs at once. It lubricates the thread so the fitting turns further before it seats, and it deforms into the spiral gap between the crests and roots so the fluid cannot follow the thread out. Because the film does not cure, the joint can be opened, inspected and re-made without wire-brushing the threads, and a roll has no shelf life to manage.

Two expectations are worth setting before you buy. Tape is a thread sealant, not a pressure-containing part: the fitting and the pipe wall carry the pressure, and no tape turns a damaged thread into a sound joint. Tape is also not a gap filler — a joint that needs tape to take up clearance will leak again as soon as the film compresses.

Low density, high density and the colour code

The roll in a plumber's box and the roll specified for a gas main look identical and are not. Density is the difference. Standard tape is soft and bulky and compresses easily, which suits water, air and general service. High-density tape is thinner and harder, holds its film thickness under torque, and is the grade used for gas, LPG and oxygen-clean lines.

Colour is the least reliable way to specify a tape: a yellow roll means "gas" in some markets and nothing at all in others. Specify density, width and standard, and let the colour follow the market. The base film is the same unsintered PTFE film used across our tape range — the difference is how the roll is processed, densified and wound.

Widths, thickness and roll length

• 12.5 mm — instrument lines and small-bore fittings up to about 1/2 in.
• 19 mm — the general-purpose width for 1/2 to 1 1/4 in pipework.
• 25 mm — 1 1/2 in and larger fittings, tank bosses and large plugs.

Thickness follows the thread rather than the pipe. A 0.075 mm film is the general-purpose choice for clean, well-cut threads; 0.1 to 0.2 mm puts more PTFE into the gap on coarse threads, large fittings and rough site work. If the fitting is unusual, send a sample — it is faster than a description. The full range sits in our PTFE tape category.

How to wrap a joint that will not leak

1. Clean and dry both threads. Tape does not bond through oil, and grit cuts the film before the joint is even hand-tight.
2. Start at the second thread. Leave the first crest bare so the cut end cannot travel into the line.
3. Wrap with the thread, not against it. Clockwise onto a right-hand thread, seen from the end that enters the fitting.
4. Three to five turns, pulled tight. More is not better: excess film holds the thread off its seat and can split a plastic fitting.
5. Bed the cut end down. Press the loose end flat and run a thumbnail around the wrap so it cannot unwind.
6. Hand-thread first, then torque to spec. Tape lubricates, so the same torque turns the fitting further than it would dry. Stop at the fitting maker's figure.

Do not use tape on flare, compression or O-ring face-seal fittings. Those joints seal on a machined face or a captured O-ring, and tape between the faces simply holds the parts apart.

Why taped joints still leak

• Over-wrapping. Too many turns hold the thread off its seat; the fitting cracks, or the joint weeps from the back of the socket.
• Wrong direction. The tape unwinds as the fitting is turned in, leaving a dry thread and a loose end inside the pipe.
• Tape on the first thread. The loose end reaches orifices, valves and instrument tappings.
• Gap filling. Tape hides a damaged thread for one assembly and fails on the next.
• Oil on an oxygen line. PTFE is compatible with oxygen; the hydrocarbon contamination that comes with a dirty roll is not.
• Re-used tape. Once compressed and unseated, the film has no memory left.

None of these are tape defects, and none are cured by buying a denser tape.

Tape, anaerobic sealant, pipe dope or hemp

For the fittings this tape is bought for, it wins on cost and on re-makeability. Where the joint is permanent, high pressure, or has to hold a vacuum, an anaerobic sealant is usually the better call.

Ordering, OEM and documentation

Rolls are supplied on 12 m spools in the three standard widths, with the cut edge held to ±0.3 mm on width and ±0.1 mm on thickness. Boxed, shrink-wrapped and blister-packed formats are all available, and printed spools and cartons can carry your brand.

• MOQ is set by width, density and pack format rather than by one figure — ask against your specification and we will quote a realistic first run.
• Private label: printed spool, printed blister card, barcode and market-specific warning text.
• Documentation: dimensional and density checks per batch; material and food-contact paperwork on request.
• Packing and export: carton and pallet details are on our packaging and shipping page.
• Production: slitting, densifying and winding run in our own Ningbo workshop.

If you are buying for a distributor rather than for a plant, tell us the market and the standard it expects. Gas tape accepted in one country is not always accepted in the next, and the difference is density and documentation, not the label. Send the spec through our inquiry form and technical sales will come back within 2 business hours.

Questions buyers ask before the first order