# propane threads

**URL:** <https://boards.straightdope.com/t/propane-threads/106602>\
**Category:** Factual Questions\
**Created:** [May 1, 2002, 1:14am UTC](https://boards.straightdope.com/t/propane-threads/106602 "2002-05-01T01:14:24Z")\
**Posts on this page:** 5\
**Page:** 1

<div class="post-metadata">

**Author:** ![SlickRoenick](https://avatars.discourse-cdn.com/v4/letter/s/e68b1a/32.png) [@SlickRoenick](https://boards.straightdope.com/u/SlickRoenick)\
**Post date:** [May 1, 2002, 1:14am UTC](https://boards.straightdope.com/t/propane-threads/106602/1 "2002-05-01T01:14:24Z")

</div>

Why are the threads reversed on propane tanks?

---

<div class="post-metadata">

**Author:** ![mangeorge](https://avatars.discourse-cdn.com/v4/letter/m/d78d45/32.png) [@mangeorge](https://boards.straightdope.com/u/mangeorge)\
**Post date:** [May 1, 2002, 1:35am UTC](https://boards.straightdope.com/t/propane-threads/106602/2 "2002-05-01T01:35:42Z")

</div>

So you can’t screw on the wrong type of regulator. I was told that this is because so many men use propane.  
Peace,  
mangeorge

---

<div class="post-metadata">

**Author:** ![DougC](https://avatars.discourse-cdn.com/v4/letter/d/7feea3/32.png) [@DougC](https://boards.straightdope.com/u/DougC)\
**Post date:** [May 1, 2002, 8:04am UTC](https://boards.straightdope.com/t/propane-threads/106602/3 "2002-05-01T08:04:54Z")

</div>

- 
  - 
    - BBQ tank connectors are reversed because they used to be about the same size as a garden hose, and reversing the threads prevented a lot of non-approved connectors from being attached. Now (in the USA) most have gone to the giant Fisher-Price damage-resistant-threads, so it’s not the issue it once was, but it still prevents lots of wrong things from being hooked up.

- With welding equipment, usually the fuel tanks all screw on normally and all the oxygen tanks are reversed because confusing the two can have dire consequences (propane is a welding gas also but it comes in a different tank for that). There are adaptors to fit anything to anything though, if you’re stuck with using nonstandard equipment and you feel lucky — a lot of welders have gone to the Big Shop In The Sky while using “cheater” adaptors. - DougC

---

<div class="post-metadata">

**Author:** ![donkeyoatey](https://avatars.discourse-cdn.com/v4/letter/d/e47c2d/32.png) [@donkeyoatey](https://boards.straightdope.com/u/donkeyoatey)\
**Post date:** [May 6, 2002, 2:05am UTC](https://boards.straightdope.com/t/propane-threads/106602/4 "2002-05-06T02:05:46Z")

</div>

> [@](#):
>
> With welding equipment, usually the fuel tanks all screw on normally and all the oxygen tanks are reversed

Not in Canada, **DougC**. Or in North America, I’m fairly certain. I can’t find a cite to state it explicitly but I think it’s an industry standard that flammable gases have left-hand thread fittings. For an oxy-acetylene torch this not only prevents the obvious hazards of having the wrong gas coming out of the valve you open, but also the oxygen bottle is at a much higher pressure (2000 psi) than acetylene (200 psi).  
Also, I’ve used an oxy-propane torch, and the propane bottle was an ordinary one. Had to use a different regulator and cutting tip, though.

---

<div class="post-metadata">

**Author:** ![DougC](https://avatars.discourse-cdn.com/v4/letter/d/7feea3/32.png) [@DougC](https://boards.straightdope.com/u/DougC)\
**Post date:** [May 6, 2002, 2:11am UTC](https://boards.straightdope.com/t/propane-threads/106602/5 "2002-05-06T02:11:55Z")

</div>

- 
  - 
    - Well I didn’t go look at mine, but ehhh, what I meant was, “normally”, like as in, ummmm -normally for _Austrailia_. Yea, that’s it. - DougC