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Is Liquid PTFE Any Good For Airlines?

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William Chitham07/06/2021 15:05:16
140 forum posts
57 photos

I've been reorganising the compressed air supply in my workshop and consequently messing about with PTFE tape. I saw a reference to liquid PTFE sealer but at £12 plus per 50ml bottle it is just above my Scrooge like just give it a punt threshold. Do people use it, is it more convenient/more efective than the tape?


Howard Lewis07/06/2021 15:19:49
6305 forum posts
15 photos

Given the cost, I would stay with PTFE tape to seal the clearance between the male and female threads.

Just wind the tape onto the male thread in the correct direction!


Steviegtr07/06/2021 15:49:02
2457 forum posts
341 photos

Yes as Howard says or you could use locktite. Not sure which one though.


Alan Wood 407/06/2021 16:23:06
236 forum posts
12 photos


SillyOldDuffer07/06/2021 17:16:07
8870 forum posts
1997 photos

I'm sold on liquid sealers because they outperform tape:

  • Easier to apply, with no chance of tearing. Much better when working upside down under a sink!
  • Flows into and fills bigger gaps than tape.
  • Mechanically stronger

Don't know how Loctite 577 compares with Liquid PTFE, but they're both based on Cyanoarcylate so similar. I'd expect a PTFE lubricated sealant to allow threads to slip slightly tighter, and the joint to be slightly easier to unscrew twenty years later!

The old recipe is green and even cheaper than tape! For the benefit of Scrooges and retro-engineers, it's Horse hair bonded with Horse sh1t...


Mark Rand07/06/2021 17:29:18
1309 forum posts
35 photos

Or 542, which is what I have a bottle of.

PTFE tape has worked very well for a long time. People get panicky about it because of the risk of getting flecks of PTFE in narrow passages etc. when the tape is over applied or on the inside of the sealed joint. Pipe dope, 'liquid PTFE' etc and so-forth are just variations on the sealant theme.

old mart07/06/2021 17:43:01
3891 forum posts
268 photos

I cannot comment on the liquid PTFE,but the Loctite is very good, I wish I had used it on the 3/4 and 1/2 steel pipework in the museum's restoration area. I used PTFE tape for all the joints and there are many leaks. Hiring a commercial quality pipe threader would have helped, but at the speed we work it would have been far too expensive, we bought a Draper set and the thread quality is not great.

martin perman07/06/2021 18:23:51
2055 forum posts
86 photos

I prefer PTFE tape, easily applied in any orientation and if would on the correct way will not leak, I've found that liquid sealants need time to cure where as the tape is instant.

Martin P

Kiwi Bloke07/06/2021 22:13:43
695 forum posts
1 photos

I don't think there's much risk of bits of PTFE tape getting into the line, provided it's applied sensibly. However, I don't like tape. How many turns do you need to apply to ensure a good seal? It's difficult to predict. How tightly do you do up the fitting? It feels as though you can just keep tightening. And then, later, as the PTFE has undergone creep, do you re-tighten the fitting because it's now looser than it was?

I've used Loctite 567 hydraulic sealant (may be an obsolete number - the tube is >10 years old, and has kept well in the 'fridge). The advantage of paste over tape is that you can be sure that the threads are filled, even if malformed or damaged. It sets firmly enough so that the fitting doesn't need to be tightened to gorilla levels of torque, which is useful in, for instance, light alloy and tapered thread fittings. It seals against low pressures instantly, and cures to be pressure-proof fairly quickly. I use it on all applications where I used to use tape, hydraulics, pneumatics, central heating. It's never let me down, whereas tape did. It's easy to undo. Only disadvantage is removing cured sealant from female threads if the joint has to be broken: it's a fiddle, it just takes time.

Edited By Kiwi Bloke on 07/06/2021 22:15:40

Oldiron07/06/2021 22:27:38
995 forum posts
40 photos

PTFE liquid is is excellent for air lines etc. I have watched many YT video's of people applying tape in the most awkward and heavy handed ways you can imagine. Most have no idea how easy tape is to apply if done properly. Most apply way too much or apply it the wrong way round. I have many a good laugh watching people trying to hold the reel with 2 hands and then roll it on the wrong way. Liquid is easy and only a very little is needed on small fittings up to 1" bsp. It will take up any gaps in the threads. Most industrial fittings are of a pretty good standard these days so the threads fit nicely. Easy to remove any excess with a rag and clean old threads with a wire brush.


Grindstone Cowboy07/06/2021 23:23:24
893 forum posts
64 photos

I've become a convert to this stuff - and it's a lot cheaper than the OP quoted.

Links to


William Chitham08/06/2021 12:44:08
140 forum posts
57 photos
Posted by Grindstone Cowboy on 07/06/2021 23:23:24:

I've become a convert to this stuff - and it's a lot cheaper than the OP quoted.

Links to


Now we are talking, that is definitely in my "take a punt" price range. Thanks to all for your thoughts.


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