Fiber or PTFE

[Prajna]

I know Plumber's Tape Fixes Everything but sometimes fiber is the correct thing to use. My understanding is that when I'm using PVC tube and plastic connectors I should use PTFE and when I'm connecting brass fittings I should use fiber but which to use if I connect, say, a brass addaptor to a PVC tube fitting? My guess is fiber because PTFE can react with brass and go hard. Amiright? Discuss.

 

[Kayos]

PTFE does not react with brass, not sure where you heard that nonsense

PTFE, fibre, rubber, hemp, paste, lsx, asbestos, plumbers mait, putty, jet blue

Use whatever makes it seal, maybe not asbestos but you might find it in old joints

 

[Prajna]

PTFE does not react with brass, not sure where you heard that nonsense

PTFE, fibre, rubber, hemp, paste, lsx, asbestos, plumbers mait, putty, jet blue

Use whatever makes it seal, maybe not asbestos but you might find it in old joints

Thanks Kram. I have both. No idea who misinformed me but I've religiously used fiber for brass ever since they said and only used PTFE on plastic on the basis that it lubricates better than fiber, to get a tighter joint.

 

[Barking Mat]

It depends how the fittings seat / mate, I find.

 

[Prajna]

It depends how the fittings seat / mate, I find.

So what are the considerations with the fit, Mat? Is there a situation where fiber is better?

 

[Barking Mat]

So what are the considerations with the fit, Mat? Is there a situation where fiber is better?

If the insert has a seat to fit into, I'd go fibre washers everytime.

Don't use rubber washers, except on gas. Gas washers obviously.

Failing that PTFE tape.

Don't consider my reply exhaustive, just my experience.

Please tell me folks, if you have a better plan.

Loctite 577 (?) On oil, diesel, hydraulics etc.

 

[Prajna]

Ah, this is all water stuff, mostly under 3 bar. In this particular instance I will be plumbing a "bailerina" wood fired water heater into 1" PVC irregation tubing. It's to seal the threads, so I'm talking old-school fiber (hemp kinda thing) that you wrap round the thread with a gob of grease. Not washers as such.

 

[Barking Mat]

Ah, this is all water stuff, mostly under 3 bar. In this particular instance I will be plumbing a "bailerina" wood fired water heater into 1" PVC irregation tubing. It's to seal the threads, so I'm talking old-school fiber (hemp kinda thing) that you wrap round the thread with a gob of grease. Not washers as such.

Yep, that works to.

Good old hemp.

 

[mike os]

Ptfe tape will do pretty much everything, use gas approved tape for gas though

Locktite 55 thread is also excellent and ime better for larger fittings

Locktite 55 works really well with rectorseal ptfe paste too

Locktite 577 will seal any metal fittings and is positional, but not for use on plastics … same as most/ all liquid sealant

 

[mike os]

@Barking Mat if you use hemp try the 55 cord, it’s really far superior for most things, but spendy but it really works

 

[Barking Mat]

@Barking Mat if you use hemp try the 55 cord, it’s really far superior for most things, but spendy but it really works

There are différent types of cord ???

 

[angellonewolf]

ptfe on every thing even if only couple wraps

 

[mike os]

There are différent types of cord ???

Just the one I think ptfe string about 2mm diameter

 

[Prajna]

Here in Portugal the guy in the plumbing shop just dumps a handful of loose hemp fibre in your hand. Actually, someone I asked to pick me some up did come back with a plastic-packed skein of it with a posh little tub of 'massa' (grease is 'massa', mass is 'massa', dough is 'massa', pastry, plaster, heard, swarm, many things are 'massa', except apples, they are 'maçã'. I find it all a bit confusing sometimes.

 

[Agroshield]

Here in Portugal the guy in the plumbing shop just dumps a handful of loose hemp fibre in your hand.

Plumbing is a very old, traditional trade. The old methods still work, but the biggest issue today is cost of labour in anything commercial. The more modern solutions, while the materials cost more, are quicker, cleaner and easier (and in some cases need less skill) to install, so the end cost is lower.

 

[voipio]

PTFE or hemp fibre are really only for joints having a tapered thread. For parallel threaded connections, the seal should be made with a suitable washer, normally a fibre washer, between the sealing surfaces (i.e. the surfaces that are pressed together when the threads are tightened), and not using the threads. Make sure the mating surfaces are clean, with no scratches across them.

 

[Prajna]

Not sure whether the threads are tapered. They certainly seem to all need sealing so I guess they are. I might have to invest in a set of thread gagues.

 

[voipio]

By tapered, the thread diameter decreases towards the end of the screw, and should be easy to see by placing something with parallel jaws onto the thread, and inline with the pipe's long axis. When a tapered joint is screwed together, it tightens up, whereas a parallel threaded joint keeps turning until the threaded end hits the "bottom" of the joint, or a shoulder hits the top surface.

See e.g. here:

Difference Between Parallel VS. Tapered Threads | RG Group

It’s still important to understand the difference between parallel and tapered threads because mixing up the two can lead to disastrous results!

www.rg-group.com

 

[Prajna]

By tapered, the thread diameter decreases towards the end of the screw, and should be easy to see by placing something with parallel jaws onto the thread, and inline with the pipe's long axis. When a tapered joint is screwed together, it tightens up, whereas a parallel threaded joint keeps turning until the threaded end hits the "bottom" of the joint, or a shoulder hits the top surface.

See e.g. here:

Difference Between Parallel VS. Tapered Threads | RG Group

It’s still important to understand the difference between parallel and tapered threads because mixing up the two can lead to disastrous results!

www.rg-group.com

Thanks Voipio, I'll take a look in a bit.

 

[Prajna]

By tapered, the thread diameter decreases towards the end of the screw, and should be easy to see by placing something with parallel jaws onto the thread, and inline with the pipe's long axis. When a tapered joint is screwed together, it tightens up, whereas a parallel threaded joint keeps turning until the threaded end hits the "bottom" of the joint, or a shoulder hits the top surface.

See e.g. here:

Difference Between Parallel VS. Tapered Threads | RG Group

It’s still important to understand the difference between parallel and tapered threads because mixing up the two can lead to disastrous results!

www.rg-group.com

All look like straight threads to me:

Experience tells me they all benefit from thread sealing though. The non-return valve (not shown) has no shoulder to seal a washer to.