PTFE Tape: How to Wrap It, When to Use It, and the Mistake Everyone Makes

You connect a radiator valve, hand-tight it, then give it a quarter turn with a wrench. Fill the system, pressurise, walk away. An hour later there's a dark stain spreading across the new plasterboard. The joint is weeping because you forgot the tape, or wrapped it the wrong way, or used it on a fitting that doesn't need it. A roll of PTFE tape costs less than a chocolate bar. The replastering costs £150. The frustration costs more.

What it is and when you need one

PTFE tape (polytetrafluoroethylene, the same non-stick material as Teflon) is a thin, stretchy white tape you wrap around male pipe threads before screwing a fitting on. As the fitting tightens, the tape compresses into the tiny gaps between the thread peaks and troughs, creating a seal that stops water or gas escaping through the thread path.

You'll hear it called plumber's tape, thread seal tape, or Teflon tape. In every UK plumbing aisle it's filed under "consumables" because you use a strip on every threaded joint and throw away the roll when it's done. But like sandpaper or masking tape, it's something you always need in the toolbox and rarely think about until you don't have one.

Every threaded plumbing connection on your project needs sealing. Radiator valve tails, isolation valves, tap connectors, boiler fittings, outside tap connections, shower valve bodies. That's dozens of joints on a typical extension. Miss one and it leaks. Wrap one backwards and it leaks. Use it where it shouldn't go and it leaks.

PTFE tape is only for threaded joints. Not compression fittings. Not push-fit. Not soldered joints. Only threaded. That distinction alone prevents more DIY plumbing leaks than any other single piece of knowledge.

Types: white, yellow, and pink

Three colours. Three different tapes. They are not interchangeable.

Standard white tape

This is what you'll use on 95% of domestic plumbing joints. A 12m roll is 12mm wide, 0.075mm thick, and costs less than a chocolate bar. Buy the WRAS-approved version (Water Regulations Advisory Scheme, the UK body that certifies products safe for use on drinking water systems) if you're working on mains-fed water supplies, which in practice means any cold water pipe in your house. Most branded tape from Screwfix or Toolstation carries WRAS approval.

Standard white tape is explicitly not rated for gas. The packaging says "Not suitable for gas" and it means it.

Gas-rated tape

Gas PTFE tape must meet BS EN 751-3:2022, the British Standard for sealing materials on metallic threaded joints in contact with gas. The tape is significantly thicker and denser than standard white tape, which is why gas rolls are typically 5m rather than 12m but cost more per metre.

The colour confusion is real. Gas-rated tape can be white. What matters is the yellow dispenser and the labelling, not the tape colour itself. Professional gas engineers confirm this repeatedly: the standard the tape meets is what matters, not whether it's literally yellow. But the yellow dispenser is a visual safety convention that prevents you grabbing the wrong roll on a busy job.

Pink and grey tape

Heavy-duty tape for industrial and high-pressure applications. Grey tape is sometimes used on stainless steel threads to reduce galling (where two stainless surfaces seize together). You won't need either on a domestic project.

How to use it properly

This is where most guides fail and most leaks start. The technique has exactly one critical rule and several important details.

The one rule: wrap clockwise

Hold the fitting so you're looking at the open end of the male thread, pointing toward you. Wrap the tape clockwise around the thread. That means the tape goes the same direction as you'll turn the fitting when you screw it in.

If you wrap it counter-clockwise, the tape unwinds and bunches up as the fitting tightens. The thread path is exposed. It leaks.

Step by step

Clean the male thread. Old tape, corrosion, jointing compound residue, pipe dope: wipe it off. A clean thread gives the tape a surface to grip.

Start wrapping at the second thread from the open end, not the first. If you start right at the tip, the tape can shred when the fitting engages and bits of PTFE end up inside the pipework. Starting one thread back keeps the tape out of the water flow.

Click to enlarge

Pull the tape taut as you wrap. Slack tape doesn't conform to the thread profile and leaves gaps. You want the tape stretched thin enough that you can see the thread shape through it.

Overlap each wrap by about half the tape width. This gives you a double layer across the thread faces where the seal actually forms.

For standard 0.075mm thin tape on a typical 1/2-inch BSP valve connection: 4-6 wraps. That's the range where the thread still engages fully but the tape fills the gaps. Fewer than 3 and the coverage is thin. More than 8 and the fitting won't screw on far enough for the threads to lock.

When you've done your wraps, snap the tape by pulling it sharply (don't cut it with scissors; the stretched break gives a thinner tail). Press the tail flat against the thread with your thumb so it doesn't flap loose and catch when you start screwing the fitting on.

Tightening the joint

Screw the fitting on by hand first. You should feel resistance from the tape after a couple of turns. Then use an adjustable wrench to tighten. For most domestic fittings: hand-tight plus a half to three-quarter turn with a wrench. Over-tightening brass fittings cracks them. Under-tightening leaves a leak.

When NOT to use PTFE tape

This is as important as knowing how to use it.

Compression fittings

Compression fittings seal through an olive (a small brass or copper ring) that gets crushed between the pipe, the fitting body, and the nut as you tighten. The seal is metal-to-metal contact, not thread sealing. PTFE tape on the olive interferes with this seal and can cause leaks.

Do not wrap PTFE tape around the olive. Do not wrap it around the pipe where the olive sits. The compression fitting was designed to work without it.

If an old compression joint weeps after re-making, a thin smear of jointing compound on the olive is the correct fix. Not tape.

Push-fit connections

Push-fit fittings (Speedfit, Hep2O) seal with internal O-rings. There are no threads. PTFE tape has no role here.

Parallel threads (BSPP)

This is the technical distinction that catches people. UK plumbing uses two thread standards: BSPT (British Standard Pipe Taper) and BSPP (British Standard Pipe Parallel). The names describe the thread profile.

Tapered threads get tighter as you screw them in. The thread itself forms part of the seal, and PTFE tape fills the remaining gaps. This is where tape works.

Parallel threads are the same diameter all the way along. They don't wedge tighter. The seal comes from a washer or O-ring compressed against a flat face at the bottom of the fitting. PTFE tape on a parallel thread adds nothing because the seal isn't in the threads.

Most domestic plumbing connections (radiator valves, tap tails, isolation valves) use tapered threads. But some fittings, particularly on imported taps and appliance connections, use parallel threads with a fibre or rubber washer. If you see a washer inside the female nut, you don't need tape. The washer is the seal.

What to buy

PTFE tape is so cheap that brand barely matters for standard water tape. The differences between a 35p roll and a 60p roll are negligible.

For standard water tape, buy a 10-pack. You'll use one roll per room on a typical plumbing project, and having a spare in the toolbox, the car, and the kitchen drawer saves a trip when something leaks at 9pm on a Sunday.

£2.5-£3 for a 10-pack of 12m x 12mm rolls from Screwfix, Toolstation, or Wickes. That works out to about 25-30p per roll.

Single rolls run £0.35-0.60 if you only need one.

Gas tape is £0.48-0.75 per 5m roll, but remember: if you're buying gas tape, a Gas Safe engineer should be the one using it.

Specific products

Any of these are fine for domestic water work:

• Made4Trade PTFE Tape 12mm x 12m (Toolstation) - WRAS approved, 0.075mm thick. Best value in a 10-pack at £2.5-£3.
• Arctic Hayes PTFE Tape 12mm x 12m (Screwfix) - widely stocked, reliable. Single rolls around £0.35-0.60.
• Essentials PTFE Tape 12mm x 12m (Screwfix, collection only) - cheapest single roll if you're already in store.
• Primaflow PTFE Tape 12mm x 12m (Wickes) - fine product, slightly more expensive because Wickes.

Don't overthink it. The technique matters far more than the brand.

Alternatives

PTFE tape is the default for homeowners because it's cheap, widely available, and works. But professionals increasingly prefer other options, and knowing what they are helps you understand what your plumber is doing (and why they might not be using tape at all).

Pipe sealing cord (Loctite 55)

Loctite 55 is a non-curing multi-filament cord coated in a sealing agent. You wind it around the thread like PTFE tape, but it has two advantages that make professionals prefer it.

First, you can back off a joint (unscrew it slightly to reposition) without losing the seal. PTFE tape doesn't recover from being unwound. If you need to angle an elbow a few degrees, the Loctite 55 joint stays sealed. With PTFE tape, you'd need to dismantle, clean, re-tape, and redo the connection.

Second, one product covers both water and gas. No need to carry separate rolls. It meets BS EN 751-3 for gas use.

The downside is cost. A 150m roll of Loctite 55 runs around £10 – £15, roughly 4p per metre compared to about 2p per metre for PTFE tape. But professional plumbers report using less cord per joint and experiencing fewer callbacks for leaks. On a single extension project, the cost difference is negligible. On a career's worth of plumbing, it adds up in the other direction.

If you're doing a full plumbing project with dozens of threaded joints, Loctite 55 is worth trying. If you're connecting a single tap, PTFE tape is fine.

Hemp and jointing compound

The traditional method. You wrap hemp fibre (a natural yarn) around the thread, then smear jointing compound over it. The compound sets semi-hard and the hemp fills the thread path.

Hemp and compound is still preferred by experienced plumbers for threads larger than 3/4-inch BSP and for galvanised steel pipe over 2 inches, where PTFE tape doesn't reliably fill the deeper thread profile. For standard domestic 1/2-inch and 3/4-inch connections, PTFE tape or Loctite 55 has largely replaced it.

Jointing compound alone

Some plumbers apply a thin smear of jointing compound (Jet Blue, Fernox LS-X, or similar) over PTFE tape as a belt-and-braces approach. The compound fills any remaining microscopic gaps. For critical connections where a leak would be particularly damaging (behind a tiled wall, under a screed floor), this combination is worth the extra 30 seconds.

Avoid Boss Green. Jet Blue or Fernox LS-X are the ones professionals recommend on UK plumbing forums.

Shelf life and storage

PTFE is chemically inert. It doesn't degrade, react with moisture, or lose its properties over time in any meaningful sense. A roll stored in a dry toolbox will work perfectly well 5-10 years later. The roll itself may get grubby or the end may be hard to find, but the material is unchanged.

Keep it out of direct sunlight (UV can eventually degrade the dispenser) and away from sharp objects that might nick the roll. That's it.

Where you'll need this

• First fix plumbing - wrapping every threaded connection on valves, tees, and fittings as the pipework goes in
• Second fix plumbing - sealing tap tails, radiator valve connections, appliance hookups, and any final threaded joints

PTFE tape appears during plumbing stages of any extension or renovation project. Every threaded joint gets taped. No exceptions.