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The world of pipe fittings

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Re: The world of pipe fittings

#71

Post by hilbert42 »

throwaway294566 wrote: post #65
SaintGhurka wrote: post #45

Earlier quoted context omitted.

"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.

You don't need oil, just rope works as well. Every DIY store (at least over here) has loose manila fibre for that purpose. Wrap into the thread, screw it together, done. The not-so-nice problem: It might leak at first. The nice feature: The fibres will soak up water (thats why oil is actually counterproductive), swell up and make a tight fit after half an hour or so. You can even readjust the angle (other than with P…

Right, there are multiple variations but they generally work in skilled hands although I learned from plumbers who always used oil (although using oil was always an imperative with gas pipes). Using oil usually negates the initial leaking whilst waiting for the hemp to dampen and swell.

Edit: I agree that using oil is counterproductive with water pipes—initially at least. I was taught by both plumbers and my father (who wasn't a plumber but a mechanical engineer who worked on power station boilers) that using oil is better in the long run as it prevents the hemp from rotting and thus premature failure of the seal. Moreover, using one oil-based method means that a plumber cannot get confused and leave oil off gas connections where it's essential.

(I'd add that when referring to oil I'm specifically referring to linseed oil (even though I've seen some plumbers inappropriately use engine oil) because it slowly polymerizes and hardens even in the absence of air. This adds to the seal's effectiveness and further protects the hemp.)

Re: The world of pipe fittings

#72

Post by everyone »

Programming is analogous to a trade like plumbing in many ways imo.

* You both design and then build a thing.

* No one else knows how it works or cares until it stops working.

* Through work you build up your own set tools and methods that you like and can apply to various jobs.

Re: The world of pipe fittings

#73

Post by PaulHoule »

agsamek wrote: post #66

This article doesn't touch much about why plumbing is hard. I'm from Poland so I'm not only IT but also a plumber ;) Plumbing is hard because it is not forgiving. It's as binary as IT except you can learn the outcome with some delay, once you learnt about a damage caused by a leak. Either you do a pressure tests right or repair can be expensive. And bugfixing is always tricky. Water also goes down whether you like it…

My complaint is that plumbers frequently do poor work for the money.

We had some come and install an instant water heater and they cut an ugly hole in the side of the house without much thought.

At one office I worked in they called Roto-Rooter (a non-union franchise that is likely to wreck your pipes and require a call to the union plumbers afterwards) who claimed that we'd flushed a condom down the drain (very hard to believe) and wrecked the pipes so we had to call the union plumber.

Another time the sink wasn't running so we called the union plumbers, they unscrewed the aerator from the faucet, saw some crud come out and the water run and left in triumph, sure of their ability to outthink a group of mere computer nerds.

Us computer nerds were sitting at the faucet immediately after that, running it and talking about it. The now aerator free faucet clogged up again within 2 minutes of the plumbers leaving.

Re: The world of pipe fittings

#74

Post by katmannthree »

hirundo wrote: post #8

"When buying male fittings, it’s best to always get tapered ones so they fit in either." I tried that with a shop compressed air system and got lot of leaks, hissing, and the compressor turning on frequently. And I never did get the system not to hiss somewhere, so I can sympathize and ditto this rant. Even when using matching fittings, with gobs of tape and/or dope, and enough force to destroy multiple fittings, it…

If you're talking about quick connects, they'll always leak a bit.

The threaded fittings however are a different story. Assuming you didn't use stainless steel on stainless steel fittings [0]:

* You can find the leaks by spraying soapy water on suspect connections and looking for bubbles (wash off and dry with clean water afterwards unless you want some serious corrosion). You can also buy a jar of noncorrosive propylene glycol based leak check fluid at your local hardware store for somewhere around $10, which is a strictly better option although it's a bit harder to clean off.

* Undo the connection and throw away every fitting you can replace (you generally should not reuse NPT threaded connections unless you know what you're doing). Clean all fittings until they look brand new and with no visible debris on/in the threads.

* Watch some videos [1] and remake the connection using the proper amount of tape and sealant and appropriate torque [2]. Only tighten the fitting. If you loosen it even a bit during the process, undo it completely. Clean both sides, reapply tape and dope, and try again. Let the sealant set ~24h and retest.

[0]: Stainless steel pipe connections are a special case because they tend to cold weld before they're fully tightened. There are ways to mitigate that but the short answer is don't use them if you don't already know how.

[1]: https://www.youtube.com/watch?v=whw9ApDJpJo

[2]: NPT connections really shouldn't be torqued (you instead use turns from hand-tight for properly cut threads) but if you're having trouble find a torque chart for your fitting material (copper, brass, steel, etc) and follow that.

Re: The world of pipe fittings

#76

Post by latchkey »

thedanbob wrote: post #6

I had a major plumbing problem some time ago (leak in the house’s main line) and paid a plumber way too much to dig a hole and fix it. I of course wasn’t about to pay him to fill the hole back up, and while it was open I took a good look. That’s when I discovered PEX. PEX is wonderful: easy to work with, inexpensive, simple to fix if you screw something up. I wish all plumbing was PEX. I briefly installed an NPT flow…

We started with welded joints, then moved to threaded (and every variation in between of that). I kind of wonder if PEX will be deprecated some day by something even better. We are going to end up with yet another standard that PEX has to interface with. Feels like an xkcd... https://xkcd.com/927/

Re: The world of pipe fittings

#77

Post by agsamek »

PaulHoule wrote: post #73
agsamek wrote: post #66

This article doesn't touch much about why plumbing is hard. I'm from Poland so I'm not only IT but also a plumber ;) Plumbing is hard because it is not forgiving. It's as binary as IT except you can learn the outcome with some delay, once you learnt about a damage caused by a leak. Either you do a pressure tests right or repair can be expensive. And bugfixing is always tricky. Water also goes down whether you like it…

My complaint is that plumbers frequently do poor work for the money. We had some come and install an instant water heater and they cut an ugly hole in the side of the house without much thought. At one office I worked in they called Roto-Rooter (a non-union franchise that is likely to wreck your pipes and require a call to the union plumbers afterwards) who claimed that we'd flushed a condom down the drain (very hard…

> My complaint is that plumbers frequently do poor work for the money.

Hehe - now you can feel like an IT customer. I think most people feel the same about IT but the domain is just more wide and prone to excuses.

Re: The world of pipe fittings

#78

Post by jcims »

hilbert42 wrote: post #42
jkqwzsoo wrote: post #9

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…

"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 de…

>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.

Re: The world of pipe fittings

#79

Post by djcapelis »

jasonhansel wrote: post #4

Conveniently, of course, the US and Canada use NPT instead of BSP, the worldwide standard. Even if an NPT fitting and a BSP fitting are the same size, one won't screw into the other, since the threads have different shapes and are at different angles.

This guy wrote a whole article outlining how bad and unusable the British pipe standards are and you’re surprised the two (ish) continents that don’t use them are actually pretty happy with their standard and don’t want the other?

NPT has some flaws and complexities but generally while it’s comprehensive conventions and practices mean that for specific types of plumbing you’ll need some specific standard fittings and once you get used to them that’s pretty much that. From gases to liquids. None of this “whoa someone decided to use a tapered one here” you don’t get to chose what fitting you’re feeling like that day, we have building codes and if it’s a pipe in a wall carrying water than there’s a convention (and likely building code) that tells you your pipe, fitting, and which way the threads should turn! (Generally in the broadest strokes: Explosive gases are reverse threaded. Everything else isn’t.)

Anyway we’ve been saying no to bad British ideas since 1776. Don’t blame us outside the Americas the rest of you (and ISO) fell for it.

Re: The world of pipe fittings

#80

Post by turdherder »

Real life licensed and certified plumber here.

Regarding the threads on common pipe fittings here in Cali: NPT threads are designed to be cut with a pitch and angle that are self sealing.

Sealing compounds can assist in the lubrication of threads to easily tighten them up but should not be absolutely necessary.

Imo it's an aid to assembly and disassembly and not always necessary depending upon the application. And in some applications it's forbidden

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