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

[RGIvy]

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

 

[Phil Pascoe]

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.

 

[RGIvy]

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?

 

[Robin Whitfield]

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?

 

[Robin Whitfield]

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.

 

[RGIvy]

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.

 

[Eric The Viking]

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?

 

[Robin Whitfield]

I get the impression that parts for LPG tend to be somewhat less leaky by default than some of the crap 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.

 

[Phil Pascoe]

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.

 

[Robin Whitfield]

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?

 

[Phil Pascoe]

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.

 

[Robin Whitfield]

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.

 

[HappyHacker]

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.

 

[Doug B]

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.

 

[Rorschach]

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.

 

[Phil Pascoe]

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.

 

[Eric The Viking]

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).

 

[Rorschach]

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.

 

[Jake]

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?

 

[Rorschach]

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.