Two different ends of the gas elbow

[john bently]

Just replacing the kitchen gas hob for a new one. It comes with a right-angled pipe (an elbow), one end of which goes into the hob and one end into the copper supply pipe.

The *threaded* part of one end of the right-angled pipe is about 4mm longer than the threaded part of the other end.

Would it be the *longer* threaded part that goes into the hob or the

*shorter* threaded part?

Since I was supplied with a rubber washer to go into the hob connection joint, should I use gas tape on both the threaded ends of the right-angle pipe. Thanks for advice.

[hrhofmann]

What is a hob?

[chaniarts]

uk-ese for kitchen stove

[JIMMIE]

Sounds like an elbow I have. The long side probably has a tapered diameter and the other side has a constant diameter. If so the tapered side screws into the black pipe and the other connects to the hob. Picture would help?

Jimmie

[Muddymike]

Your messing with gas not knowing what you are doing probably justifies the rules of gas fitting only being done by qualified engineers. Do your family a favour pick up the phone and call a "Gas safe" gas fitter.

Mike

[jamesgangnc]

You probably ought to check the instructions, they might say. The end that goes into the stove probably is not tapered thread if it has a washer that sits under it. In that case you would not use tape. Tape is only for "pipe" thread. Pipe thread tapers and achieves a seal by the threads themselves. On that you do use tape or dope. If you really have soft copper pipe coming in for the supply you may need an adapter between the elbow and the copper so you can use a compression fitting on the copper. If that's the case carry the elbow down to a friendly local hardware shop and ask for help :-) Here in the states we usually have black iron pipe for supply at it does have tapered thread but I know you guys and the canadians use copper sometimes. Nothing wrong with copper but your stove might be geared towards the way we do it.

[Stormin Mormon]

In the US, where I am. Natural gas is a low enough presure, that the folks I work with coat the external (male) threads with a bit of Rectorseal #5. We do not use teflon tape on gas threads. Risk of some of the tape flaking off, and get into the gas valve, and create more problems.

Can't comment on the long or short ends of the elbow. Try both -- see which works better.

[JIMMIE]

Ooops, left out connects to hob via flexible pipe. Anyway it sounds like the long side of the fitting is for iron pipe and the other for flexible copper tubing via a compression fitting or a flare fitting. This may mean the elbow was either intended to connect the supply to the flexible copper pipe or the hob to the flexible copper pipe.

hope this helps

Jimmie

[David Nebenzahl]

On 2/19/2010 2:48 PM Stormin Mormon spake thus:

Who is this "we" of whom you speak?

Honestly, every plumber I know uses teflon tape. I know there's other stuff available, and I'm sure it works, but were does this stuff come from all of a sudden that "nobody used teflon tape"?

Hell, use old-fashioned pipe dope for that matter. It all works.

And another thing: what's the big deal about the "correct" tape for gas (the yellow stuff)? Again, maybe it's better, but everywhere I go I see white tape on joints in gas piping. And none of it leaks.

Sheesh.

[JIMMIE]

I tried Rectorseal for the first time this week replacing my brittle PVC greenhouse sprinkler system with galvanized and PEX. No leaks first time and easier to apply than tape.

Jimmie

[terry]

And that's how the language changes! 'Hob' also common, in North America, where wood stoves were used (and even after that when some such stoves were converted to dual fuel) wood/oil. Also common expression where a kettle of hot water was kept 'on the hob'. And as in saying "Come on in out of the cold and have a cup of tea/coffee; the kettle is on the hob". The term was also occasionally applied to a swinging bracket on some stoves on which the kettle was placed after it had boiled, to keep it hot or simmering. Younger generations and/or the less well read, brought up with electricity probably unlikely to be familiar with the term 'hob'. Wife's grandmother who died at 101 in the 1970s would refer to her wood stove as having four 'hobs'; these were the round metal sections/ covers in the heavy cast iron metal stove top that one would lift to expose bottom of cooking pot to direct heat. She was a smart woman but if one used a term such as 'data' or 'cyber' she wouldn't be be familiar.

[Bod]

The yellow tape (for gas fittings) is thicker. The white is for water. The reason is, that the white tape can suffer from osmosis, in other words, the gas can slowly permeate through the tape. It is only a very,very tiny leakage and probably almost undetectable by sniffing, but that's the reason.

Bod

[Stormin Mormon]

We means all the gas fitters I've met, and discussed the question with. Since natural gas is very low pressure, the teflon tape really isn't needed. And it risks having part of the tape flake off, and get into the gas valves. The yellow tape is supposed to be thicker. But, with the lower gas pressure, it's not really needed.

[Joe]

If a plumber showed up at one of my projects with Teflon tape in his kit, he'd be shown the door. Same thing for a finish carpenter with Plastic Wood in his toolbox. Sign of a competent journeyman is using the best, not 'quickie' materials.

It comes from plugged gas valves, faucet strainers with bits of Teflon tape stuck in the screens, and in other trades, failed engines with bits of Teflon tape stuck in oil passages.

But the Teflon filled variety is much better.

If you had a detector similar to those used for Freon, you'd find that, indeed, it does leak, although not to a critical extent. Local gas company here apparently not using it, so it may not be universal.

Joe

[Chewbacca]

Actually a hob is just the 'hot plates' so usually just that with the oven & grill etc in a separate unit

[JIMMIE]

Yep, my grandmother was Irish, she grew up in England though moved to US in 1919. I remember her having a wood stove an electric stove and her gas hob.

Jimmie

[Heliotrope Smith]

David Nebenzahl wrote in news:4b7f46db$0$3261$ [e-mail]:

Not sure if you are refering to states side or not but here in Britain the "yellow" tape refers to the colour of reel. The gas tape is white but much thicker than the water MDFE tape and the regulations permit only a single wrap of tape on the gas threads whilst between 10 and 20 turns is not uncommon on water threads.

"Old fashioned (gas) pipe dope" is widely used but may not be used in conjunction with tape.

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[Stormin Mormon]

First, I use teflon tape in some instances.

Second, I'm told that the white teflon based pipe dope dries out and gets crumbly. Much better to use Rectorseal, or the blue stuff.