# Liquid PTFE any good? ... better than tape?



## RGIvy (6 Oct 2020)

Any comments on the best PTFE - is it tape or liquid?
I've run out of liquid and wondering if I should use tape (I have plenty) or buy more liquid. Having asked the question, I've never had a leak from using liquid PTFE - but same for tape (if done properly). I just wonder if liquid is more forgiving as if there is a "leak" the liquid is pushed into a better seal.

Rog


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## Phil Pascoe (6 Oct 2020)

I've not noticed a difference, but I use the liquid in places it's near impossible to get tape - it's very good for that.


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## RGIvy (6 Oct 2020)

Phil Pascoe said:


> I've not noticed a difference, but I use the liquid in places it's near impossible to get tape - it's very good for that.


Which one is your go-to?


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## Robin Whitfield (6 Oct 2020)

I use Jetlube sealant as well as tape but have never used the liquid PTFE adhesive. Tape is significantly better for things like outside taps on a pre-fitted backplate where you want that interference fit to enable the tap to not be upside down.
I use Jetlube when using plastic fittings (water filters etc) where the PTFE tape rarely likes to seal and if you stick too much on you end up cracking the fitting/stripping the threads. It's also very useful if you're doing something like re-using an olive when replacing a stop-tap or similar. Clean up the pipe and olive with some scotch brite and then a bit of jetlube helps to ensure no leaks when you're putting it back together onto the new mating surface.

What do you use the liquid PTFE for?


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## Robin Whitfield (6 Oct 2020)

It's worth also noting that you can get tape in a range of different thicknesses, with the thicker stuff generally being preferable to many many wraps of the thin stuff as it's easier to apply consistently.

Then there's stuff like the Loctite 55 sealing cord which some people swear by, but I've never found a need.


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## RGIvy (6 Oct 2020)

Robin Whitfield said:


> What do you use the liquid PTFE for?


Mostly for the LPG pipes in my motorhome, but also for my compressor fittings. Not done water plumbing for ages.


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## Eric The Viking (6 Oct 2020)

On correctly made plumbing fittings, some threads are straight but some taper. I find the PTFE tape is very good for tapering threads (such as outside taps as above and radiator bungs/valves, etc.), but not so wonderful for parallel threads. Thicker PTFE tape is supposedly for gas fittings, but both seem to be good as long as you get the right amount on the thread. I never have success using it with straight threads though.

For olives I'm old fashioned and use BossWhite (on the inside pipe surface and the base of the olive only, not the actual thread as that isn't the seal). It has the big advantage that it cleans off completely if that is needed, and it does make a good seal. I also use it on the copper-piped solar system we have, where it seems to work well with flat mating surfaces as an adjunct to a fibre washer (on the flow meters). There the temperature cycling is pretty extreme - can be more than inside the boiler.

I've recently gone over to Fernox's LS-X instead of the other PTFE goos that I've tried. It works well and doesn't seem to gum up in the tube like others do - but it's not cheap.

Horses for courses?


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## Robin Whitfield (6 Oct 2020)

I get the impression that parts for LPG tend to be somewhat less leaky by default than some of the rubbish plumbing parts out there these days, although the rating of up to 0.3mm on some I just looked up does seem like it'd be plenty for water fittings too.

I actually started using Jetlube after a gas installer was using it on a friend's boat. BossWhite sounds like something pretty similar?



> on the inside pipe surface and the base of the olive only, not the actual thread as that isn't the seal


Oh absolutely. I've on occasion used a light oil on old threads (such as when replacing a pump but not the isolators) but just as a lubricant to help get it all tight though.
The number of flexible tap couplers that you find with fibre/rubber washers that have been tightened up onto quarter turn compression isolators with mountains of PTFE tape around the threads is unreal though.
I *have* connected a coupler to an isolator in this manner before but I flattened the end of the isolator with a file/diamond stone first (so that it mated with the washer rather than cutting through it) and didn't use any PTFE.


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## Phil Pascoe (6 Oct 2020)

I tend only to use the liquid when the joint is a little inaccessible. For bibcocks (of my own) I take the innards out of the tap, put the tap in the correct position on the back plate and solder it, fixing it to the wall in one piece. No movement, no leaks.


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## Robin Whitfield (6 Oct 2020)

Phil Pascoe said:


> I tend only to use the liquid when the joint is a little inaccessible. For bibcocks (of my own) I take the innards out of the tap, put the tap in the correct position on the back plate and solder it, fixing it to the wall in one piece. No movement, no leaks.


I suppose if the tap innards fail you can take the tap apart on the wall and replace?


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## Phil Pascoe (6 Oct 2020)

There's nothing much to fail other than washers (which of course are destroyed if you leave then in situ while soldering) and the fixing solid of the tap doesn't affect that.


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## Robin Whitfield (6 Oct 2020)

Phil Pascoe said:


> There's nothing much to fail other than washers (which of course are destroyed if you leave then in situ while soldering) and the fixing solid of the tap doesn't affect that.


A bit more to go wrong with ones with check valves in them I presume? I think the ones I tend to install have plastic parts that have to be removed from the threaded back thinking about it.


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## HappyHacker (6 Oct 2020)

I used liquid PTFE once, came to change the fitting a few months later the PTFE had set rock hard and was better than epoxy at fixing the parts together. Never been near it since. Bosswhite or PTFE tape for me. I have some drinking water safe stuff I thought was similar to Bosswhite but it does not stick and is a pain to use so I don't.


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## Doug B (6 Oct 2020)

I tend to use Boss universal jointing compound for most things as it’s suitable for potable water & gas, I was taught ptfe was only for taper threads so only really use it for radiator fittings.
I guess I’m old fashioned but for straight threads I still use hemp & jointing compound.


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## Rorschach (6 Oct 2020)

Eric The Viking said:


> On correctly made plumbing fittings, some threads are straight but some taper. I find the PTFE tape is very good for tapering threads (such as outside taps as above and radiator bungs/valves, etc.), but not so wonderful for parallel threads. Thicker PTFE tape is supposedly for gas fittings, but both seem to be good as long as you get the right amount on the thread. I never have success using it with straight threads though.



What straight threads have you come across that need PTFE? Straight threads aren't used for sealing fittings, that's what tapered threads are for.


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## Phil Pascoe (6 Oct 2020)

HappyHacker said:


> I used liquid PTFE once, came to change the fitting a few months later the PTFE had set rock hard and was better than epoxy at fixing the parts together. Never been near it since. Bosswhite or PTFE tape for me. I have some drinking water safe stuff I thought was similar to Bosswhite but it does not stick and is a pain to use so I don't.


I had the opposite - I used it by mistake for threadlock and didn't notice, their both being blue and wondered why days later the "threadlock" hadn't gone off.


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## Eric The Viking (6 Oct 2020)

Rorschach said:


> Straight threads aren't used for sealing fittings, that's what tapered threads are for.


I know, but often nowadays cheap fittings have straight threads where they should taper. For example the 1" BSP to 15mm compression fittings sold by two major "sheds" should taper, but don't. I ended up using 15mm bath tap fittings, grinding down the lip of the flange that takes the fibre washer and then using that (with a smear of BossWhite, IIRC) on the flange of the male fitting it was coupling to. The grinding down bit was so it didn't hit the male fitting before the fibre washer did.

The "adaptors" would have been impossible to seal without soldering them. This I considered, but the "male" side was a flowmeter with a glass insert and a plastic indicator - couldn't prevent those overheating.

I can't remember actually using tape on a straight thread - that wasn't the point I was making (clumsy use of English on my part). The trouble is having to dream up effective bodges for incorrectly made parts - those flowmeters and adapters should have had one side tapered, and because they didn't I couldn't use the "correct" approach (which would have involved PTFE tape, or hemp).


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## Rorschach (6 Oct 2020)

Eric The Viking said:


> I know, but often nowadays cheap fittings have straight threads where they should taper. For example the 1" BSP to 15mm compression fittings sold by two major "sheds" should taper, but don't. I ended up using 15mm bath tap fittings, grinding down the lip of the flange that takes the fibre washer and then using that (with a smear of BossWhite, IIRC) on the flange of the male fitting it was coupling to. The grinding down bit was so it didn't hit the male fitting before the fibre washer did.
> 
> The "adaptors" would have been impossible to seal without soldering them. This I considered, but the "male" side was a flowmeter with a glass insert and a plastic indicator - couldn't prevent those overheating.
> 
> I can't remember actually using tape on a straight thread - that wasn't the point I was making (clumsy use of English on my part). The trouble is having to dream up effective bodges for incorrectly made parts - those flowmeters and adapters should have had one side tapered, and because they didn't I couldn't use the "correct" approach (which would have involved PTFE tape, or hemp).



The BSP part didn't taper? Take it back, it's not BSP without a taper to it lol.


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## Jake (6 Oct 2020)

Rorschach said:


> The BSP part didn't taper? Take it back, it's not BSP without a taper to it lol.



You need another letter, BSPP or BSPT?


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## Rorschach (7 Oct 2020)

Jake said:


> You need another letter, BSPP or BSPT?



You are correct, I do, as the OP stated though he was expecting a tapered thread on the part he ordered and it didn't have it, so it was defective. But thanks for the correction, don't want others to get confused.


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## Eric The Viking (7 Oct 2020)

In the interests of accuracy, I think it was actually 3/4" BSP (female) to 15mm compression. I do tend to get 3/4" and 1" muddled up because of the ID and OD measurements (no longer do plumbing very often these days). Sorry. 

It wasn't how it was specified (precious little info available on the supplier's web page), but the function it was supposed to serve. In context it was illogical to make an adapter with a parallel thread, as it couldn't be effectively sealed. I didn't say it was "defective" as such, just not correct/usable. The threaded socket was also far too deep, but couldn't be hacksawed down because the spannerable bit was narrow and on the extreme outer end. 

In the past I have been driven to alter stock fittings (using a router table as I don't have a lathe), to make adapters where none were available (this one was beyond me however).


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## Robin Whitfield (7 Oct 2020)

I've faffed trying to find/modify similar sounding parts in the past, generally finding it easier to replace the part that it was meant to be connecting to rather than creating some monster adapter that never wants to seal.

You see it regularly with coffee machine connections trying to connect them to standard appliance taps when there's a pump and filter involved. Speaking of which, I've got such a mess (not installed by myself I might add) to sort at some point. It's been weeping for over 2 years now with no huge issues though so it tends to be a job floating around the bottom of the list. I think I even purchased the parts to fix it sometime last winter...


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## Steve_Scott (7 Oct 2020)

Rorschach said:


> What straight threads have you come across that need PTFE? Straight threads aren't used for sealing fittings, that's what tapered threads are for.


Quite right... a parallel threaded connection should not have the water seal made on the threads, but rather a sealing face should be provided to facilitate the use of a washer/o-ring.


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## Steve_Scott (7 Oct 2020)

Eric The Viking said:


> It wasn't how it was specified (precious little info available on the supplier's web page), but the function it was supposed to serve. In context it was illogical to make an adapter with a parallel thread, as it couldn't be effectively sealed. I didn't say it was "defective" as such, just not correct/usable. The threaded socket was also far too deep, but couldn't be hacksawed down because the spannerable bit was narrow and on the extreme outer end.



There are British/EU standards for thread dimensions on plumbing fittings. If I recall correctly, there is a minimum thread/throat depth but no maximum defined in BS EN 1254-4. Even so, you tend to find manufacturers don't offer you much more brass than they can get away with! A mating male thread should either be parallel and shorter such that an external washer can be used before the fittings bottom out, or you could use a taper male thread and sealant (I am a convert to loctite 55 but I'm not a fan of introducing circumferential stress into brass parts as its inviting SCC failures when plumber's over-tighten the fittings).


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## cammy9r (8 Oct 2020)

I use PTFE on parallel threads as its a lubricant too. Allows a nice bind free nip up on the olive or whatever. Taper threads get Loctite 55. I have standard thin tape, thicker gas tape and liquid and the 55 and use whatever I see the job needs. Also have boss white and green to hand too.


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## Dave Moore (8 Oct 2020)

RGIvy said:


> Any comments on the best PTFE - is it tape or liquid?
> I've run out of liquid and wondering if I should use tape (I have plenty) or buy more liquid. Having asked the question, I've never had a leak from using liquid PTFE - but same for tape (if done properly). I just wonder if liquid is more forgiving as if there is a "leak" the liquid is pushed into a better seal.
> 
> Rog


We use Loctite 55 ptfe string at work, it’s better than liquid and tape. It is impregnated with a sealant which goes off once fitted. We buy ours from BSS for about £10 but it goes a long way.


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