[jkqwzsoo]

In case anyone from the US reads this, BSPP and BSPT fittings are rare and incredibly frustrating here, as our NPT (National Pipe Taper) threads are different and the selection of BSP(P/T) fittings is extremely poor in comparison.

Also, I work with NPT fittings quite a lot:

> For what it’s worth, I tightly wrap the tape 10 times round the male thread and get an enraged mountain gorilla to tighten it up.

This is a WTF NO!!! for NPT and I’ll assume a WTF NO!!! for BSPT as well. You need about 1.5 wraps of PTFE tape to seal a fitting. Any more is wasteful and asking for leaks (or damage, if you’re using plastic fittings). It helps if you use the correct tape width for the fittings (1/4”, 1/2”, and 1” for me) and develop a wrapping method that keeps the tape under tension at all time and in such a direction that threading it into the fitting doesn’t unwrap the tape.

Also, in my experience, when someone inexperienced first learns what pipe tape is, they try to apply it to everything. 20 wraps around a tapered pipe? Wrap a Swagelok fitting? Try to make a butt joint or an adapter for two pieces of plastic tubing? I’ve seen it all.

[hilbert42]

"You need about 1.5 wraps of PTFE tape to seal a fitting. Any more is wasteful and asking for leaks"

I would have thought this obvious and it's essentially my experience (and I'm definitely not a plumber). However, I've found that more PTFE tape is needed on old or worn fittings or on ones that have damaged or badly cut threads—or when mating same sized pipes/fittings but each with different threads (yes, that's a desperate brute-force move in an emergency but I've had to force such matings on more than one occasion). In these circumstances, I'll use two or three turns or more often by trial and error—and this changes somewhat depending on whether I'm using thinner white PTFE tape or the thicker pink one.

Of course—not being plumber—it often happens that when I urgently need PTFE tape I cannot find it (it having been filed in some obscure place that I've forgotten about—even though I keep a reasonable stock of it), it's then I fall back to the good old combination of Hessian/burlap jute-type rope (of which there is always some lying around in my workshop) and linseed oil based paint. It's messy and much less convenient combination than PTFE tape but it still works wonderfully well. Moreover, it's more tolerant of the amount applied as the linseed oil actually binds to the pipe surface as opposed to the more 'mechanical' bond of the PTFE.

[jcims]

>Of course—not being plumber—it often happens that when I urgently need PTFE tape I cannot find it

Ahh, young padawan, the way of the elder is to buy a roll every time you have a project to do until you have achieved saturation...where there is a lightly used roll of teflon tape in every drawer and on every surface of your workshop and garage.

[SaintGhurka]

"combination of Hessian/burlap jute-type rope (of which there is always some lying around in my workshop) and linseed oil based paint."

Could you explain that? How do you seal pipe fittings with rope?

Edit: found an explanation. TIL that you can use the fibers just like tape and wrap the threads.

[mgarfias]

A small quibble: the tape don’t seal. It’s a lubricant for the threads wedging together to seal.

For a REALLY good primer on the subject, read Carrol Smith’s _Nuts, Bolts, Fasteners and Plumbing Handbook_ (aka Screw to Win).

[kortex]

> the tape don’t seal.

No, the tape absolutely contributes to the seal. Sure, the lubrication lets you thread more tightly without binding, but that's not to say the tape isn't contributing to the seal. If it didn't, you would still have a spiral leakage path. PTFE tape is soft enough that it deforms and prevents the spiral leakage path which can occur with any tapered threaded joint.

I've actually used PTFE tape in super high pressure situations (>1000 psi) with straight (un-tapered) joints (you aren't typically supposed to, but this was for an experiment), and it indeed sealed.

> The tape also works as a deformable filler and thread lubricant, helping to seal the joint without hardening or making it more difficult to tighten

https://en.wikipedia.org/wiki/Thread_seal_tape

[johnwalkr]

Such a great book. I’m a mechanical/aerospace engineer and it’s astounding how many in my field don’t understand fasteners and tend to oversize them. It’s seen as conservative but it can actually backfire.

[pengaru]

> For a REALLY good primer on the subject, read Carrol Smith’s _Nuts, Bolts, Fasteners and Plumbing Handbook_ (aka Screw to Win).

+1 for anything by Carrol Smith

Back in my gearhead days Engineer To Win was a near constant fixture next to the toilet.

[kennend3]

As someone who is NOT a pipe fitter but lived with one for many years.. It was odd reading this and I'm glad someone like you responded to correct things.

> For what it’s worth, I tightly wrap the tape 10 times round the male thread and get an enraged mountain gorilla to tighten it up.

Again, not a pipe fitter but this just screams "WRONG". If someone needs to use that much force to tighten it up, one can only assume that the pipe is now so full of tape it simply doesn't fit?

My roommate had a "unlimited BTU" gas fitter license (Canada Class "A") and this for a living and preferred "pipe dope"

"Pipe dope is generally stronger seal than Teflon tape, which is why plumbers and other professionals use it rather than tape for seals that are permanent."

[rsync]

"My roommate had a "unlimited BTU" gas fitter license (Canada Class "A") and this for a living and preferred "pipe dope""

I do this kind of thing a lot as we own and maintain our own water plant. My preferred sealant is the yellow PTFE tape that is used for natural gas.

It is quite a bit thicker than the white tape, it sticks to threads better and it is easier to work with, in terms of manual dexterity.

I never use the white tape for anything.

I don't like pipe dope at all and I only use it for large fittings that are going to be buried or inaccessible.

ALSO, helpful hint: If you are mixing plastic pipe (like schedule 40/80) and metal pipe, always have metal female couplings and plastic male couplings. A metal male going into a plastic female is one tighten away from cracking the plastic.

[dsfyu404ed]

>"Pipe dope is generally stronger seal than Teflon tape, which is why plumbers and other professionals use it rather than tape for seals that are permanent."

They use it because it's faster. As long as it's good enough any performance difference is secondary.

[aidos]

I think there’s cultural difference where the tongue in cheek context has been lost a bit.

They probably use neither 10 full wraps, nor an enraged mountain gorilla, but then I’ve seen stranger things in plumbing.

[quietbritishjim]

Except in the next sentence he says that he doesn't really use a gorilla (and that's the bit that's obviously a joke). But he doesn't say he doesn't use 10 wraps.

[lazide]

It’s hard to tell the difference between a frustrated home owner/part time plumber and an enraged silver back I guess.

At least one of them is vegetarian?

[fuzzfactor]

The lowland gorilla comes to mind . . .

[mannykannot]

What do you think of the advice that it is acceptable to use a tapered male thread in a straight female one? My guess is that if you do that, you have at best one turn of the thread helix holding them together and providing a seal (and perhaps you would be trusting in nothing more than the tape jammed between the threads if you used ten turns of it!)

[johnwalkr]

I don’t think it’s acceptable. Maybe works in pinch to get through a weekend but I would always replace it with a proper fitting. Plus if you damage the female threads or o-ring seat, you’ve made a much worse problem for yourself.

[balls187]

> Also, in my experience, when someone inexperienced first learns what pipe tape is, they try to apply it to everything.

That’s me. Whoops.

[VLM]

Tape causes massive contamination problems with fuel and hydraulic systems.

Its not that the Teflon reacts with hyd oil, its that the inevitably little tiny bits of stuff physically jam/ruin seals and clog nozzles.

[rdl]

Ugh, I applied it to PVC pipe, which made it leak, sigh.

[hattmall]

The real pro-tip is not to use tape at all. Instead use pipe dope or joint compound, it's cheap, easy, and better in every possible way. If you only have two do one or two very low importance joints, like a showerhead then tape is fine. But for anything serious use the joint compound. If you are doing a lot of work it's absolutely a game changer.

[bdowling]

> This is a WTF NO!!!

I’m pretty sure the author was exaggerating, because no sane person would use an enraged gorilla to tighten fittings. Gorillas are simply far too dangerous to be trusted with important plumbing work.

[klyrs]

If you think plumbers are expensive, you've never tried to hire a gorilla for an hour.

[robk]

This is more useful than Teflon tape I find https://www.amazon.co.uk/Loctite-K97870-Henkel-Sealing-Multi...

[jve]

Thanks for mentioning this. This is so easy and fast to work with and you usually end up with sealed joints (Sorry, I'm an amateurish DIYer, first tries were failing). No additional grease needed to reduce friction, withstands high temps, for water and gas. What's not to love? Price maybe.

[shellfishgene]

In Germany using hemp fibers instead of the PTFE tape is still really common (together with a sealing paste calle Neo-Fermit). The disadvantage of the tape is that you can't turn the fitting backwards even a little bit when tightening it, or you get leaks. With hemp that does not matter so much as it swells up with water.

[azalemeth]

I particularly hate the confusion that BSP and NPT cause. They're almost interchangeable (differing, iirc, probably on the angle of flank) and will get about three turns in and then leak or fail under pressure. In my world, this has led to graduate students spraying liquid nitrogen around. It's clearly the case that the two probably were supposed to be identical but diverted due to manufacturing differences in the distant past.

The standard advice I've been given when it comes to either vacuum or cryo fittings is "cut anything American off it as soon as it arrives and put DIN standard or KF kit on as soon as possible". Standards are a pain and that xkcd about there being too many of them is very, very true.

[iancmceachern]

Little nit pick. BSP is British.

[dsfyu404ed]

Your comment reeks to high heaven of textbook engineer. The practices you advise do not survive in a world of bottom dollar commodity pipe fittings.

Everyone with dirty fingernails knows that 3-4 wraps is a pretty good rule of thumb for fittings that are meant to go together and you need more when you're mix and matching BSP and NPT threads because you have a larger leak path to take up.

Nobody bothers stocking multiple widths of tape. That only makes sense in a production environment where you're only ever working with one size and can build to it.

In a pinch you can "augment" things like compression fittings with tape on the OD of the ferrule.

[kortex]

> You need about 1.5 wraps of PTFE tape to seal a fitting.

Not a pipe fitter, but I've done a lot of plumbing on a huge variety of systems (sinks, drains, air lines, HPLCs and other chemistry equipment, bioreactors, RO systems, potato cannons). I have found through experience that the thick PTFE tape (usually grey or yellow) is almost always superior to the thin tape. I use 2-3 wraps of that and that seems to be ideal.

Thick tape is also a lot easier to remove than the thin PTFE if you have to reinstall (you aren't supposed to re-use tape if you unscrew it).

[berjin]

If you want a really good seal you wrap the tape 1-2 overlaps at the start of the thread and progressively make it thicker and thicker so you have more overlaps (10x) at the base. I guess it depends on the fittings but some run out of tapper and you can't tighten it anymore without the hexagonal nut hitting the adjacent fitting. This works well as you're building your own tapper which is sort of acting as an o-ring.

Generally BSP male fittings are always tapped which is why they don't mention it.

[jakewins]

Do you have a reference for this? Everything I've read is the purpose of the tape is to reduce friction (hence PTFE), not to actually seal. In other words, the seal comes from the fittings connecting tightly, made possible by 2-3 wraps of PTFE low friction tape.

[TheJoeMan]

> when someone inexperienced first learns what pipe tape is, they try to apply it to everything

I just removed some from a medical oxygen DISS fitting, which is a conical seat on the inside meaning the threads do 0 sealing duh-oh.

[sokoloff]

I use a minimum of 4 wraps and usually 5 or 6 wraps on black pipe in the 3/4”-2” range. 2 wraps might be enough for nice clean plastic or brass threads in the 1/2” or less range, but larger steel fittings need more PTFE tape.

[PaulDavisThe1st]

Pipe dope FTW.

[jnellis]

Indeed. If your threads are new you're not supposed to use any teflon tape, you use pipe dope. Teflon tape is for worn threads when you are out of pipe dope.