CAN YOU USE PTFE TAPE ON GAS CYLINDER CONNECTION?

Feb 10, 2013
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Can one use PTFE tape to ensure a gas-tight fit on the cylinder union? The brass hose-to-cylinder connection never seems competent enough to me. Yes, I take care of my brass hose coupling, but the cylinders must get plenty of abuse from previous owners? Even the slightest dinge (technical term?) on the cylinder coupling could allow gas to escape.

Certainly, there have been a few times that I've had a whiffy gas locker - even though it's vents are clear and hose etc is new. A dealership once told me that "you have to really nip the nut up tight with a spanner". Well, I've given my spanner and nut plenty of 'Isaacs' and even hung off it a-la Robin Knox Johnston! BUT a brass- to-brass connection seems doomed to fail at some stage, especially with road movement and metal-metal imperfections.

I'm aware that there's two different types of PTFE - one for general plumbing and one for gas. Sooo, apart from getting over-zealous with tape and blocking up the aperture, is there any reason why tape can't be used
 

scotjimland

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No.. do not use PTFE on a bottle seal..

the seal on a propane bottle is a brass, face to face seal.. the thread does not make the seal..
As the bottle seal is female connection.. it is unlikely and unusual for it to be damaged..
the seal on your pitail or regulator, which is male, is far more likely to get damaged..

Inspect the male, if it is scored either replace or if only minor scratches, try rubbing with some very fine emery cloth..
 
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Oct 1, 2007
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I always assumed you shouldn't

As the faces of the joint

Are ground to fit each other

tape on the thread won't stop gas coming from
The inner gas carrier pipe on the connection

Only my thoughts
 

Terry

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Well I disagree with Jim on this :D cannot see what harm it can do and yes use the gas stuff --I would buy yourself a can of gas leak detector spray as well --I know I have given some of my own bottles plenty of torques but still detected the odd wiff of gas in the locker ---The gas SS pipe I just got off Tecno has a rubber connection on the bottle side and hand tighten knob/no spanners so I cannot see why no PTFE
I can stand to be corrected it won't be the first time :Dedit I am assuming you mean on the threaded bits
terry
 

Gromett

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I was always led to believe no PTFE on any gas connection. Plumbed in my whole van 3-4 years ago and no problems at all.
Occasionally got a smelly bottle before I started on the refillable, but a quick tweak always sorted it.
 
Mar 23, 2012
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Can one use PTFE tape to ensure a gas-tight fit on the cylinder union? The brass hose-to-cylinder connection never seems competent enough to me. Yes, I take care of my brass hose coupling, but the cylinders must get plenty of abuse from previous owners? Even the slightest dinge (technical term?) on the cylinder coupling could allow gas to escape.

Certainly, there have been a few times that I've had a whiffy gas locker - even though it's vents are clear and hose etc is new. A dealership once told me that "you have to really nip the nut up tight with a spanner". Well, I've given my spanner and nut plenty of 'Isaacs' and even hung off it a-la Robin Knox Johnston! BUT a brass- to-brass connection seems doomed to fail at some stage, especially with road movement and metal-metal imperfections.

I'm aware that there's two different types of PTFE - one for general plumbing and one for gas. Sooo, apart from getting over-zealous with tape and blocking up the aperture, is there any reason why tape can't be used

The seal is the face of the domed end so ptfe wont help it might mean you cant tighten the connector fully so no (in my opinion).

David
 

scotjimland

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The seal is the face of the domed end so ptfe wont help it might mean you cant tighten the connector fully so no (in my opinion).

David
you have it in one.. (y)

There is another valid reason for not using PTFE tape,
If a small part of it gets into the pipework it can block the regulator or a gas jet causing all sorts of problems..

PTFE should only be used on taper threads where it is used as a lubricant and sealer.. taking great care not to wrap it over the edge of the thread where it could break off when tightened. .. (see above).

Never use on parallel threads or gas compression joints .
 
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Jaws

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No. one son is a gas safe approved fitter.
I asked him about this a while ago.
There is a specific type of ptfe tape made for gas joints and ordinary white stuff should not be used ( an installation will fail commissioning tests if it is used and they will not issue a Gas Safe certificate )

But as others have already mentioned, the seal is on the domed end not the thread
 

Terry

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The gas PTFE IS BLUE -still don't see any reason it cannot be used on the threaded bits -we always use gas it paste on any of the compression /olives joints but that stuff is red and gets everywhere -I have several mates who are gas safe reg and I admit I did not know they even did a gas PTFE tape until a couple of yrs ago -so will ask them about it's use
terry
 

Plumberman

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Hi Wingman,
PTFE tape should not be used on Gas Unions as there is a risk if it stopping the two machined faces of the union sealing properly.
Also as posted earlier there is a risk of causing a blockage in the connecting pipe work / fittings.
You can use an approved LPG jointing paste if you have problems with leaks but be careful not to get any inside the pipe work ,just a very light coating should do the job.
PTFE is only a thread sealing tape.
If you smell gas in your Gas locker buy a can of leak detection spray which is quite cheap from a plumbers merchants and will detect where the leak is coming from.
Leaks will show up by foaming bubbles around the leaking areas,even micro leaks can be dangerous if allowed to build up.
Don't be tempted to use washing up liquid as an alternative as this has been proved to be corrosive to hoses and fittings .
This should be used every time you undo or disturb a fitting.
LPG is heavier than air so gas will collect at the lowest point,which is why you should have drop holes under all cylinders and appliances which should be kept clear of debris at all times.
Also the base of cylinders should be kept clear as this is an integral part of the surface area of the cylinder to allow gas to be drawn off at the correct rate.
The sealant mentioned by Terry in previous post is Stag Red Sealant and is for use on permanent joints not cylinder unions .
Most modern sealants are non setting to allow for easy removal of fittings.
Hope this helps you.
Alex.
 
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OP
wingman
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Thanks Alex and all other contributors. Really interesting replies.
When I'd sat down and thought about it, all made complete sense, doh!

What was equally interesting (and quite a gem) was the locker space itself. I've always understood about keeping the vents clear and I have two contoured platforms for the cylinders BUT, I have a bad habit of using the locker to bung all sorts of stuff. As of now, I've stuffed in levellers, a flat hose reel, dust sheet to kneel on and an adjustable parrot-nosed spanner contained in anti-rattle bubble wrap to give the nut a few more Newtons!!! The locker's not full, but the advice about an air flow around the bottles is something I've never thought about!

Bugger; where am I going to put this stuff now???

Thanks guys
James
 

Terry

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Can't remember ;)
Spoken to 3 different gas safe plumbers now and all say it's safe to use on the threaded bit ---It is now white tape but comes with a yellow top and is slightly thicker than normal PTFE, normal ptfe which incidentally is pressure tested up to 20 bar where gas is normally at 2 bar at the most -All 3 said gas is measured in millibars unlike water and all said it was OK to use or use the paste just be careful not to get the paste into the pipe :)All said use the leak detector spray after making the seal if you are unsure,
terry
 

funflair

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I think the question has to be WHY would you want to put ptfe tape on the thread as it will not help with a gas seal, if the male into female joint is leaking the threads are not there to stop it as gas would still get up the inside of the nut.

To lubricate the threads OK.

Martin
 

mentaliss

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Can one use PTFE tape to ensure a gas-tight fit on the cylinder union? The brass hose-to-cylinder connection never seems competent enough to me. Yes, I take care of my brass hose coupling, but the cylinders must get plenty of abuse from previous owners? Even the slightest dinge (technical term?) on the cylinder coupling could allow gas to escape.

Certainly, there have been a few times that I've had a whiffy gas locker - even though it's vents are clear and hose etc is new. A dealership once told me that "you have to really nip the nut up tight with a spanner". Well, I've given my spanner and nut plenty of 'Isaacs' and even hung off it a-la Robin Knox Johnston! BUT a brass- to-brass connection seems doomed to fail at some stage, especially with road movement and metal-metal imperfections.

I'm aware that there's two different types of PTFE - one for general plumbing and one for gas. Sooo, apart from getting over-zealous with tape and blocking up the aperture, is there any reason why tape can't be used
Well can't speak for the others BUT GasLow ( my system) technical says absolutely not !!!! no tape, no sealing gue..........
 

gasman2008

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If you suspect a leak cover the joint with leak detection fluid, if you want to help the seal put a small (VERY) amount of gas tap grease (this must be for 3rd family gas) on the male end before you put the hose onto the bottle
 
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Spoken to 3 different gas safe plumbers now and all say it's safe to use on the threaded bit ---It is now white tape but comes with a yellow top and is slightly thicker than normal PTFE, normal ptfe which incidentally is pressure tested up to 20 bar where gas is normally at 2 bar at the most -All 3 said gas is measured in millibars unlike water and all said it was OK to use or use the paste just be careful not to get the paste into the pipe :)All said use the leak detector spray after making the seal if you are unsure,
terry
Given that these gas safe plumbers have no idea about cylinder pressures I wouldn't put too much store in anything they say. Were they qualified to work with LPG? Not all are I believe.

I vote NO too. As has been repeatedly said, the threads don't make the seal.
 

scotjimland

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Tyres????? :whistle::whistle::whistle:

thanks for your valuable input to this discussion. :RollEyes:

Shall we have a vote?
No tape !
I don't need a vote on the OP question.. no more than you would need to vote on the correct procedure to connect / disconnect a lead acid battery

I spent ten years in the oil and gas industry maintaining and installing high pressure LPG instrumentation.. , flow, pressure, density, temperature and level instruments. (high pressure means in excess of 3,000 psi.... over 206 bar ).
I was employed by AMOCO on an American owned and operated platform in the N Sea. PTFE tape was not allowed off shore as it had been directly responsible for an accident on a refinery in the US..
 

vwalan

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gas safe dont cover m,homes anyway ,private ones .. or at least they didnt used to .has it changed .?
 

dave newell lvs

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You could use tape if you wanted to but you really shouldn't. As others have said the seal is made at the dome end into the inner face of the POL valve, or by a rubber seal if its a continental/ refillable/butane type nut fitting.

The three gas safe fitters need to go back to school! Propane LPG is stored at around 6 bar (100psi give or take) only downstream of the regulator is measured in millibar. Gas PTFE tape is exactly the same stuff as ordinary plumbing PTFE tape (the clue is in the name P poly T tetra F fluoro E ethylene) but is twice as thick, its white and comes on a yellow reel.

Vote=NO!

D.
 
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Dave Newell is spot on, PTFE tape is designed to work with taper threads not parallel threads.
Also absolutely do not swing on a spanner when tightening the joint, these sealing joints are made face to face hardening down won`t do anything other than stretch the threads.
Some machined faces have a flexible gasket or copper washers, again a quarter turn when tight is all it takes to seal the joint anymore, and you are just over compressing the gasket.
Obviously any high pressure joints will be tightened down to a pre-determined torque setting.
 
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Gas Safe do cover residential park homes and Leisure accomodation vehicles and boats I know cos I got it, I dont use Ptfe on machined faces or bottle threads
 
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You could use tape if you wanted to but you really shouldn't. As others have said the seal is made at the dome end into the inner face of the POL valve, or by a rubber seal if its a continental/ refillable/butane type nut fitting.

The three gas safe fitters need to go back to school! Propane LPG is stored at around 6 bar (100psi give or take) only downstream of the regulator is measured in millibar. Gas PTFE tape is exactly the same stuff as ordinary plumbing PTFE tape (the clue is in the name P poly T tetra F fluoro E ethylene) but is twice as thick, its white and comes on a yellow reel.

Vote=NO!

D.
The pressure varies with temperature and can get a lot higher than 6bar. On a hot day in Spain say it could be double that.

Tim
 

Plumberman

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I am a fully qualified engineer in natural gas LPG propane / butane/ and have been for 30 years. I understand the working pressure of natural gas and LPG .
If you do not want to take the information on board that is your problem,
You are all dealing with a gas more dangerous than natural gas with no qualifications.
Don't want to enter into an argument with funsters about gas issues but you are messing about with a potential explosion.
I am qualified in leisure accommodation vehicles,park homes ,in both NG & LPG.
Not trying to be clever but that is what I do for a living.
Also the pressure delivered in a motorhome could never be more than 37 mb for propane and 28 mb for butane on a supply from a cylinder.
The pressures you quote are for a bulk tank installation which are considerably higher pressure until controlled by opso and an upso shut off.
Operation of an opso is between 70 -80 mbar and a upso if the outlet pressure falls below26-28 mbar.
 
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wingman
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Blimey! I've really set one running here!!

As an aside, I road tested the new travelling gas BBQ out tonight. You'll be pleased to know that as advised, I used NO tape, gunk or jointing compound! Got a cylinder out of the van, linked it up to the BBQ, gave the nut plenty of Newtons with a spanner, checked for leaks with brush and washing up liquid (yeah I know someone here advised against, but that was the manufacturers destructions) and hey presto - no gas smell.

I did notice however that even when I got the brand new regulator and hose out of the box, it seemed to smell. Maybe I'm confusing gas smells with rubber?
 
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