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Tightening gas filler hoses


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I have been trying to find the correct methods to tighten the filler hoses on a refillable gas system but there is a lack of information about this on any of the main suppliers web sites (Gaslow, Gas-it etc.).

The hose fitting appears to be a 3/4" UNF with 45 degree flare angle (I measured the flare angle myself and I may be out by a degree or two). If correct, this would make it a SAE J512 and not a JIC (SAE J514) as advertised. A JIC fitting is specified to have a 37 degree flare angle. The only reason why this may be important is that these have different tightening torques.

Does anyone know (definitively) what these fittings are, or what torque should be used to tighten these?


As a second question - is it ok to use a thread locking compound on these fittings? I thought about using a drop of Loctite 242 or Tru-blu just on the threads to prevent them coming loose under vibration (not on the face seal or the first thread)

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GOOGLE-ing using "refillable gas bottle 3/4" UNF JIC” as the search-term indicates that the JIC fitting is the norm for the inlet of refillable LPG bottles/tanks. Regarding Gaslow and Gas-it fill-hoses, it’s also specifically said (Fill Hoses and Pigtails section) here




including the advice that "Fill hoses (only) use a metal-to-metal seal, no washers are supplied or needed for these on either brand.”


I have a Gaslow R67 “Direct Fill” bottle and obtaining a gas-tight seal between the filling-adapter and the bottle’s filler-inlet required substantial ‘torquing’. This isn’t too surprising with a metal-to-metal joint and (because I was filling via an adapter not a filler-hose) it was obvious when further tightening was needed to obtain a proper seal.


There does not seem to be any evidence that the inlet-fitting is not the advertised JIC type and (Dare I say it?) I very much doubt that DIY or professional installers will much care about tightening torques - they’ll just do up the fitting pretty tightly and then check for leaks afterwards. I can’t see any problem with your suggestion to use a thread-locking compound if you are concerned about vibration, and I guess you could also (carefully) use a gas-seal compound on the metal-to-metal seal if you were really worried about gas-leakage.


Have you contacted Gaslow and Gas-it? The suppliers of these refillable systems should be in the best position to comment on the inlet-fitting type, torque values, and the advisability of using sealing and/or thread-locking compound or PTFE tape.

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It is of paramount importance that the tapered mating faces match each other. I do not know how the OP measured the taper, but I have discovered the following simple method.


Cut a small strip of card so as to have an included angle to be checked at one end. Place the tapered end of the card against the tapered part of the fitting. The card should then line up parallel to the threadof the fitting.

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The OP could test the integrity of the filler hose connection by pressurising it from an external gas cylinder.


Gaslow sell a hose which connects between an external gas cylinder and the fill point. It would then be just a matter of dabbing soapy water around the joint with an artist's brush and checking for bubbles.


I bought one of these hoses for just that purpose, plus I can attach a Gaz 907 bottle as a backup supply between refills.

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plwsm2000 expressed suspicions that the ‘flare’ on whatever make of filler-hose he eventually bought




MIGHT not be the JIC fitting that Gaslow and Gas-it advertise they use. Obviously that’s possible, but it’s far more likely that even refilling-hoses not sourced from Gaslow or Gas-it will still use the JIC fitting so that they can properly connect to a refillable LPG tank/bottle.


A filler-hose deliberately made with the SAE J512 fitting would (presumably) need to be paired to an LPG tank/bottle with an exactly matching filler-inlet to meet the criterion Alanb mentions that the tapered faces of the filler-inlet and filler-hose end-fitting must mate perfectly.


There can’t be many filler-hoses for leisure-vehicle refillable tanks being marketed in the UK and, as the Galow and Gas-it hoses are apparently interchangeable, I’d expect hoses (Are there any?) from other providers to have the same interchangability and, hence, use the same JIC end-fitting.


I’m not sure if connecting an external LPG bottle to the filling-point would replicate the high pressure produced when gas in liquid form is delivered to the motorhome by an LPG pump. In any case the onboard refillable bottle/tank will need to be filled initially, at which time a leak-test can be carried out.

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Thanks for the replies.

I have an Alugas system (bought as a kit) and I can confirm that this is a SAE J512 (also know as SAE 45°) and NOT JIC (SAE J514).


I measured the male parts on the filler Tee piece, the UK filler bayonet part and the Alugas cylinder with a digital angle guage and they all read 45 degrees. I also measured the females on the hoses by taking an imprint with a bit of plasticine and measured that too and it is also a SAE J512. I also confirmed this with the Alugas suppliers.

I called Gaslow and they say theirs are JIC which means that the Gaslow filler parts are NOT compatible with Alugas fillers even though (to an untrained eye), they look the same and have an identical thread so will go together. I also emailed GASIT tech support with the same question and will update this post when I get an answer. This could create a problem when you get around to replacing the hoses after 5 years or so.


As other posters have said, it is important that both faces mate together on a metal-metal seal. If you do mix JIC and SAE 45 and torque them up, you will damage the faces and it may not seal properly. That said, these fittings are designed for working pressures of 5,000 psi which is somewhat greater than the 50-250psi of propane vapour, so you may "get away with it" (for a while at least!).


I would still like to apply somewhere near to the correct torque on these fittings although the recommended 50N.m (for JIC) and 45N.m for SAE 45 may be difficult to achieve without over stressing other parts due to the reaction force (the torque for the brass UK bayonet hose needs to be 70% of these figures). As you will probably need a 22mm crowfoot adaptor for your torque wrench, I'll see what this translates to using the "flats" method which is much easier to use. (The "flats" method means tighen by hand (no spanners) and then count how many flats on the hex nut are needed to be turned through using a spanner). According to what I have gleaned, this should be about 1 to 1 1/2 flats.


On the subject of checking for leaks, how many people check this during the hot summer months? The vapour pressure of propane varies considerably with temperature (50psi at 0degC to 200psi at 45degC approx.) so it might be possible to have no leaks in the winter but have a small leak in the summer. Has anyone experienced this?




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Regarding the 37 and 45 degree versions of these fittings it's quite common for the female socket to have a '37/45' seat these days and to thus be compatible with both 37 and 45 degree male fittings. The most recent JIC filler hoses that I bought were so equipped although the male end has I think to be one angle only, 45 degrees in this case.


I have to put my hands up and admit that I knowingly mixed 37 and 45 degree fittings when I did the install on my current van. It all nipped up just fine and although there is a risk of damaging the male brass fitting on the bottle by attaching a 37 degree fitting such as a tee piece to it's unlikely if you're going to do it up once and not touch it again. It tests fine too; no detectable leaks and there is still pressure in the filler hose weeks after refilling.

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It might be worth asking Autogas 2000 Ltd about the filler-hose fitting and the torque requirements.


This company markets various makes of refillable bottle including Alugas products




It also markets flexible filler-hoses with a length ranging from 0.5m to 2.0m




but there’s nothing to indicate that these differ according to the make of the refillable bottle.


Gaslow’s installation instructions are here




and no torque datum is recommended for the filler-hose-to-bottle joint. I’d be surprised if even a ‘professional’ installer would torque that joint to a specific Nm figure, and more surprised still if the average DIY-installer would have a tool suitable to carry out that task (or even consider that this might be necessary).


This link refers to the various fitting types




The 'Flats From Finger Tight’ tightening ploy is also described, but I note that the example applies to steel fittings.

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I thought I would post a final update with my conclusions based on my discussions with Alugas, Gasit and Gaslow.

Both Alugas and Gasit use the 45 degree flare angle SAE J512 fittings for the filler hoses while Gaslow use JIC (37 degree flare angle SAE J514). This was confirmed after speaking to each of the suppliers technical people who were familiar with the different specifications.

As mentioned previously, at first glance they look the same and have the same thread, but they are not compatible with each other. Be aware of this when you get around to replacing your hoses etc.


I used a small drop of tru-blue (http://www.toolstation.com/shop/Plumbing/d20/Plumbing+Consumables/sd2711/Tru+Blu+Pipe+Thread+Sealant/p40236) to help prevent the threads from coming loose under vibration. This was ONLY appied to the thread and not the face seal (it is not used as a sealer in this application).




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