PTFE tape on water fittings: when to use it and how to wrap it

PTFE tape is the thin white tape plumbers wrap round threads. It is cheap and useful, but it is often used on joints that do not need it, and sometimes on joints where it causes a leak. This guide covers water fittings only.

This guide is not for gas. Gas pipes, gas fittings, boilers and gas appliances must only be worked on by a Gas Safe registered engineer. Do not use anything here on a gas fitting. See when to call a Gas Safe engineer.

What PTFE tape does

PTFE (polytetrafluoroethylene) tape is a thin, non-sticky film. Wrapped round a male thread, it fills the tiny gaps between the threads and acts as a lubricant, so the joint can be screwed up tighter and comes apart more easily later. White tape sold for plumbing is for water. Check the reel or product page says it is suitable for drinking water: in England and Wales, materials in contact with drinking water have to meet the Water Supply (Water Fittings) Regulations, and a WRAS listing is one way a maker shows that.

Where it is used on water fittings

PTFE tape helps on joints where the thread itself makes the seal, typically:

• tapered threads, such as some male iron (BSP taper) threads into brass fittings;
• threaded adapters and plugs where there is no washer or O-ring;
• the thread of an outside tap screwing into a wall plate elbow, where the maker says to seal the thread;
• some radiator valve tails and bleed valve threads (on a water heating system, not gas).

Always check the fitting maker's instructions. Many modern fittings say exactly how they should be sealed.

Where not to use it

• Compression olives. A compression joint seals because the brass olive is squeezed between the nut and the fitting body. Tape is not what makes it watertight. Tape on the olive can stop it seating evenly. If a compression joint weeps, the usual fixes are a gentle extra nip with a spanner, or a new olive, not more tape. Some plumbers put tape or jointing compound on olives as a habit; follow the fitting maker's instructions rather than habit.
• Joints with a washer. Tap connectors, flexible hoses, toilet fill valve connections and washing machine hoses seal on a fibre or rubber washer against a flat face. Tape on the thread does nothing useful and can stop the nut pulling the washer down.
• Push-fit fittings. These seal on an internal O-ring. Tape on the pipe can stop it seating. See push-fit vs compression vs solder.
• Plastic waste traps. These seal on a washer or cone. Hand tighten them; no tape.
• Anything with an O-ring, unless the maker says otherwise.

How to wrap it

1. Clean the thread. Remove old tape, compound and grit with a dry cloth or a small brush. Make sure the thread is dry.
2. Start one or two threads back from the end. This keeps loose tape out of the water flow, where it can block a valve or a tap aerator.
3. Wrap in the same direction you will tighten. Looking at the end of the male thread, wrap clockwise for a normal right-hand thread. Then when the fitting screws on, it smooths the tape down rather than rolling it off.
4. Keep it taut and overlapping. Pull the tape slightly as you go so it beds into the threads, overlapping each turn by about half.
5. How much? Enough to fill the threads and make the joint feel firm as it tightens, not so much that the fitting will not start on the thread. On a typical 1/2in thread that is usually a handful of turns. If the fitting is hard to start, take some off.
6. Tear it off and smooth it down with your fingers, then screw the fitting on by hand before finishing with a spanner.

If you wrap the wrong way, the tape bunches up as you tighten. Take it off and start again.

Tape, compound, or both?

Plumbers sometimes use a jointing compound (a paste) instead of tape, or as well. On drinking water pipework, use a compound that says it is suitable for potable water. Compounds sold for heating systems or other trades are not always suitable for drinking water. If you are not sure, ask at the counter or check the maker's data sheet.

Before you start

Isolate the water at the nearest isolation valve or the stopcock, and have a towel and a bucket ready. PTFE tape is part of a basic plumbing tool kit.

PTFE tape at Wickes

We haven't tested this. Figures are as the maker states them (checked 13 November 2026).

Which way do you wrap PTFE tape?

Clockwise, looking at the end of the male thread, for a normal right-hand thread. That is the same direction the fitting turns when you tighten it.

Should I put PTFE tape on a compression fitting?

Not as a rule. The olive makes the seal. If a compression joint leaks, try a small extra turn, then a new olive.

Can I use PTFE tape on a gas pipe?

Do not work on gas pipes or fittings yourself. Gas work in the home must be done by a Gas Safe registered engineer.