PTFE on Isolation Valve

You are carrying out some work at home and have seen that some people recommend using PTFE tape on compression fittings and other people swear against it. This has been a contentious debate even among professional tradesmen since before time began.

Okay, maybe not that long ago but at least since PTFE tape has been around which is quite some time. The question we get asked is whether you should use PTFE tape on compression fittings?

To answer that question, this article will explore PTFE tape, its uses and whether or not it can be used on compression fittings.

What is PTFE Tape?

PTFE tape (polytetrafluoroethylene) is also known as Teflon tape or plumber’s tape and is a type of thread lubricant used for waterproofing and to prevent threads from seizing.

It was originally used in the military to make machinery run more smoothly by reducing friction between moving parts. However, due to its water sealing properties, it has been adapted for many other applications including plumbing fittings and sealing joints on fuel lines.

What is PTFE Used for in Plumbing?

In plumbing, PTFE tape is used to wrap around threaded parts of a pipework connection to create a seal against leakage.

PTFE tape is extremely flexible and waterproof making it perfect to wrap around and press into the threads of plumbing fittings. Once the thread is then done up, the threaded part of the connection also becomes sealed preventing any water from escaping.

Should You Use PTFE Tape on Compression Fittings?

On NEW compression fittings, PTFE tape is NOT REQUIRED although there are many people that still use it as an added layer of protection against leaks.

With old fittings, PTFE tape is needed to help seal the joint but the key thing here is not whether PTFE tape should or should not be used, it is how the PTFE tape is applied, especially on cheap or older fittings where the olive cannot be removed.

How to Apply PTFE Tape to Compression Fittings

PTFE tape can be used for compression fittings but not in the regular way that you are likely to see PTFE tape used in plumbing.

In the case of a compression fitting, the PTFE tape is wrapped around the leading face of the olive to help create the watertight seal. Do not apply PTFE around the thread – the thread is there to enable the compression and will not be the cause of a leak itself.

Also, do not use too much PTFE tape, this could be counterproductive and prevent the joint from sealing at all.

PTFE Tape on Packing Nut

Another way to use PTFE tape is on certain types of packing nuts such as the one you will find on a lockshield valve to save time in draining the entire system. Pull off about eight inches of the tape and twist it so it appears like a piece of string. Then after removing the packing nut, wrap it around the stem of the valve and poke down with a tool such as a bradel.

Can You use PTFE on Isolation Valves?

If you have had to change an isolation valve at any point and been unable to remove the olive and decided to reuse the union nuts that are already there… A good thing to do would be to use some PTFE tape as outlined above.

A good couple of wraps around the leading face of the old olive will go a long way to preventing the new isolation valve from leaking.


PTFE tape can be a lifesaver, but should you use it on compression joints? The answer depends on where you intend to use it and also how old the fittings are.

If you plan to use PTFE on the threads then do not bother as it will not serve any purpose but if the fitting is particularly old, some PTFE tape around the olive can save you lots of time and money.

Plumbing Wizard Tips

“Wrapping compression joint threads with PTFE is a waste of time!”

“On old joints, wrap PTFE around the leading face of the olive to help you create that seal!”

“An alternate to using PTFE tape on compression joints is to use some Boss White jointing compound!”

“If you are unsure of what to do with your compression joints, call out a professional to do it for you!”

Frequently Asked Questions

Can PTFE Tape be Used on Gas Fittings?

Gas rated PTFE tape is available although it differs slightly from PTFE used in water applications. Gas rated PTFE tape tends to be much thicker and denser.

Can PTFE tape be used on petrol?

Yes, PTFE tape is resistant to petrol and is often used on fuel lines.

Can you use too much PTFE tape?

Yes, using too much PTFE tape can cause your joint to not be closed enough to create a watertight seal.

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