How can I cure my gravity circulation problem?

[SJB060685]

Yes makes perfect sense.
Like you said its not really needed to go into such detail but I'm the sort of person who doesn't like not knowing something exactly. If something like this pops up I will go and have a read through and mock up some rough figures just to get a feel for it

 

[Neville Hillyer]

Is the ~ 0.5M horizontal section of pipe hot right up to the coil inlet?.
You might also consider isolating the coil and install a 600 mm (spool) piece of pipe between the flow&return and see if you get thermosyphon circulation.

At the end of the day, if all else fails would you consider a pumped solution?.

The flow is about 40cm and the return is about 50cm to the tank connections.

Not as easy as it sounds but is is possible. However, I already have excellent thermosyphon circulation through the bathroom radiator. An easier trial would be to temporarily join the two pipes at the small header tank.

As indicated I would be very reluctant to abandon gravity circulation especially as it has worked well for 50 years.

 

[John.g]

I don't think joining the pipes at the header tank is a good idea as there will be virtually no static head at this point but as you stated there is excellent circulation through the rad and one might expect the flow pipe to be hot almost right up to the coil connection due to thermosyphon circulation within the pipe itself.

 

[SJB060685]

@Brambles can you say to me which units you were using during your rough calculations for the above required pressure.

 

[Brambles]

For the Darcey Weisbach

V m/second
p kg/m3
L m
D m

For the Reynolds Number:

V m/second
D in mm
For density / viscosity at 60 degrees C for water use 3.1m

 

[SJB060685]

Thanks. Without that there was no way I could knock up some rough numbers

 

[Brambles]

P is calculated in N/m2

1 inch of head (water) is around 250 N/m2

 

[SJB060685]

Yes 1 N/m2 equates to 1 Pa. 1 bar equals 100 N/m2 or 100,000 Pa

 

[Brambles]

No, 1 bar = 100,000N/m2

 

[John.g]

I get the gist of what is being discussed above but it must be remembered that the gravity driving force available is only determined by the flow/return temps and the head available.
If one realistically accepts a max head of 2.5M and a flow/return temp 75/15C with a cold cylinder and 75/60C when hot, then the max circulating force is 0.061M/2.42ins and the min is 0.021M/0.84ins. A pumped system with a differential head of 3M will give a flow rate factor of X12 in the first case and X7 in the second case and that is one and the main reason that pumped systems are now almost universal. I do have a vague memory (50 years) of some gravity driven heat exchanger with a huge finned coil.

 

[Brambles]

John G,

I fully agree. The calculation may reveal the cause, but it contributes very little to delivering hot water !

 

[John.g]

I don't think the calculation reveals the cause, gravity fed systems have been delivering hot water for hundreds of years?. Pumping the above system may and probably will give hot water but a gravity system was specified.

 

[SJB060685]

Yes Brambles, that was a typo error.

 

[Brambles]

It’s not a typo - the calculation is showing that the coil inside diameter needs to be around 28mm for the gravity and temperature generated pressure differential to be greater than the Installed pipe (and coil) resistance.

 

[SJB060685]

It’s not a typo - the calculation is showing that the coil inside diameter needs to be around 28mm for the gravity and temperature generated pressure differential to be greater than the Installed pipe (and coil) resistance.

No you misunderstood me. I said that was a typo to your reply where I mistakenly said 100 n/m2 equates to 1 bar. As I said above 1 bar = 100,000 Pa or should have read 100,000 n/m2. It was late and I missed out some noughts.

 

[John.g]

Brambles, can you please give me your calculated flow and resistance for the installed coil, preferably with the resistance in M.
[automerge]1589800269[/automerge]
My own basic calcs would indicate that 5.8M of 22mm ID pipe should flow ~ 7.5 LPM @ 0.061M head which should satisfy the requirements except that the corrugations are having a huge effect but even if they do then there should be some reduced level of performance.

 

[Neville Hillyer]

Brambles, can you please give me your calculated flow and resistance for the installed coil, preferably with the resistance in M.
[automerge]1589800269[/automerge]
My own basic calcs would indicate that 5.8M of 22mm ID pipe should flow ~ 7.5 LPM @ 0.061M head which should satisfy the requirements except that the corrugations are having a huge effect but even if they do then there should be some reduced level of performance.

I would prefer a better source than Amazon but it appears that corrugated pipe is specified in the old British way ie by internal diameter. The following is an example from: https://www.amazon.co.uk/Corrugated-Stainless-Steel-Pipe-DN25/dp/B07B2JVJFX

Nominal width: DN25
Wall thickness: 0.20 mm
Inner diameter: 25.5 mm
Outer diameter: 31.8 mm
Bending radius: 39 mm
Operating pressure: 10 bar

This appears to be compatible with my specification to Telford and my 1 inch (28mm) pipes. What was not clear to me was the use of corrugated pipes to replace my original standard coil.

I had hoped that somebody would say they had some experience of the use of corrugated coils in a gravity system.

I am trying to compile a full list of possible reasons for the replacement cylinder not getting any heat. Here is my list so far:

1 - Partial or total blockage which allows full heat to bathroom radiator but no heat to cylinder.

2 - Incorrect or imprudent connections to cylinder.

3 - Partial blockage inside cylinder which still allows it to be flushed.

4 - New cylinder fails to self-clear air locks like all earlier cylinders did.

5 - Corrugations inhibit upward air flow in the face of static or slow downward water flow.

6 - Slight slopes on 'horizontal' pipes more critical than previously.

I suspect that if the cylinder fails to self-clear air locks then it will be a continuing source of trouble in the future. My experience is that large old vented systems can slowly suck in small quantities of air at any time.

 

[SJB060685]

My experience is that large old vented systems can slowly suck in small quantities of air at any time.

In an ideal system any air or dissolved oxygen within the system is usually expelled to minimal amounts within a few months, thereafter any remaining is only enough to slightly corrode any ferrous materials. Air should ideally not be drawn in, unless you drain down for maintenance or a pump is sucking it in somewhere.

 

[John.g]

I would prefer a better source than Amazon but it appears that corrugated pipe is specified in the old British way ie by internal diameter. The following is an example from: https://www.amazon.co.uk/Corrugated-Stainless-Steel-Pipe-DN25/dp/B07B2JVJFX

Nominal width: DN25
Wall thickness: 0.20 mm
Inner diameter: 25.5 mm
Outer diameter: 31.8 mm
Bending radius: 39 mm
Operating pressure: 10 bar

This appears to be compatible with my specification to Telford and my 1 inch (28mm) pipes. What was not clear to me was the use of corrugated pipes to replace my original standard coil.

I had hoped that somebody would say they had some experience of the use of corrugated coils in a gravity system.

I am trying to compile a full list of possible reasons for the replacement cylinder not getting any heat. Here is my list so far:

1 - Partial or total blockage which allows full heat to bathroom radiator but no heat to cylinder.

2 - Incorrect or imprudent connections to cylinder.

3 - Partial blockage inside cylinder which still allows it to be flushed.

4 - New cylinder fails to self-clear air locks like all earlier cylinders did.

5 - Corrugations inhibit upward air flow in the face of static or slow downward water flow.

6 - Slight slopes on 'horizontal' pipes more critical than previously.

I suspect that if the cylinder fails to self-clear air locks then it will be a continuing source of trouble in the future. My experience is that large old vented systems can slowly suck in small quantities of air at any time.

You say that you flushed all sections of the pipework, if this didn't include the coil then you should do this. If the coil is clear then IMO, your options are to either fit a cylinder/coil like your previous one or at least one with a self supporting non corrugated coil, the other option is one that I suggested before, install a pump (like the one I suggested) on the flow side, this pump cannot, as I thought, be set down to 0.1M head but can be set to a PP (proportional pressure) setting of 0.5M, at this setting if still no flow (for whatever reason) it will ramp down to a minimum of 0.25M at zero flow which can be read off in the form of the power consumption, this, again IMO, may give you a big stick to beat some body with and, at the very worst, provide you with a spare circulating pump.
[automerge]1589834818[/automerge]
Came across a few readings that a neighbour gave me a few years ago from his standard hot water cylinder which he converted to fully pumped from gravity when he changed his boiler. If his readings were accurate then he seems to have been getting ~ 1.5 LPM at 50C continuously in gravity mode only with 19mm ID flow&return.

 

[Neville Hillyer]

Many thanks to all who have contributed to this thread and given such helpful advice.

Having considered all the evidence and advice my view is that it may be most profitable to initially investigate a permanent 15mm link between the mains and the cold feed from the small header tank. With suitably placed isolation valves this could provide mains flushing as and when required.

I plan to:

1 - Isolate the bathroom radiator, cylinder and pump to flush around the gravity circuit.

2 - Open the cylinder coil valves and hope to get a sufficient reverse flush up the coil to remove any air locks.

Since I will be doing this while positioned near the small header tank I will be able to see:

1 - Any debris.

2 - Air - this will require a short temporary hose or pipe to take the vent below water level.

The above may take a while but I plan to keep this thread updated.

 

[Brambles]

No you misunderstood me. I said that was a typo to your reply where I mistakenly said 100 n/m2 equates to 1 bar. As I said above 1 bar = 100,000 Pa or should have read 100,000 n/m2. It was late and I missed out some noughts.

My apologies and again to get to 20 characters!
[automerge]1590003167[/automerge]

Brambles, can you please give me your calculated flow and resistance for the installed coil, preferably with the resistance in M.
[automerge]1589800269[/automerge]
My own basic calcs would indicate that 5.8M of 22mm ID pipe should flow ~ 7.5 LPM @ 0.061M head which should satisfy the requirements except that the corrugations are having a huge effect but even if they do then there should be some reduced level of performance.

Ok, so for 22mm ID at 7.5lpm, that will equate to a velocity of around 0.33m/second.

If you run the two equations and consider the coil length is 8m. The minimum head required for the thermosyphon to operate at that velocity is 2.4 inches of water or 0.061m of water.

This may be on the low side depending on the friction factor if the pipe coil is corrugated on the inside.

The above only calculates the force required to drive the flow at 7.5lpm through the coil - it does not allow for the interconnecting pipework.

As stated earlier, for a 28mm dia coil at the same velocity, the force required is significantly lower

 

[John.g]

Still, one would expect some flow through that coil, corrugated or not, with reduced output, but not zero, it will be very interesting to see Neville's results.

 

[Brambles]

John,

Yes, I fully agree - I have learn’t quite a lot from this exercise!

 

[Gasmk1]

I am still going for partially blocked cold feed where the cylinder is if his drawing is correct

 

[SJB060685]

John,

Yes, I fully agree - I have learn’t quite a lot from this exercise!

I've learned a lot as well. Up until this dilemma ive never needed to do these calculations.

 

[Brambles]

You never should need to - it is a theoretical exercise anyway unless you know the friction factor of the coil.

My view is that identifying the cause will not change the most cost effective remedy of converting to a pumped system.

With respect to Telford, I have always found them very responsive and quick to offer a substantial discount against the delivered item that I was unhappy with ( rather than to collect and replace).

 

[John.g]

I would prefer a better source than Amazon but it appears that corrugated pipe is specified in the old British way ie by internal diameter. The following is an example from: https://www.amazon.co.uk/Corrugated-Stainless-Steel-Pipe-DN25/dp/B07B2JVJFX

Nominal width: DN25
Wall thickness: 0.20 mm
Inner diameter: 25.5 mm
Outer diameter: 31.8 mm
Bending radius: 39 mm
Operating pressure: 10 bar

This appears to be compatible with my specification to Telford and my 1 inch (28mm) pipes. What was not clear to me was the use of corrugated pipes to replace my original standard coil.

I had hoped that somebody would say they had some experience of the use of corrugated coils in a gravity system.

I am trying to compile a full list of possible reasons for the replacement cylinder not getting any heat. Here is my list so far:

1 - Partial or total blockage which allows full heat to bathroom radiator but no heat to cylinder.

2 - Incorrect or imprudent connections to cylinder.

3 - Partial blockage inside cylinder which still allows it to be flushed.

4 - New cylinder fails to self-clear air locks like all earlier cylinders did.

5 - Corrugations inhibit upward air flow in the face of static or slow downward water flow.

6 - Slight slopes on 'horizontal' pipes more critical than previously.

I suspect that if the cylinder fails to self-clear air locks then it will be a continuing source of trouble in the future. My experience is that large old vented systems can slowly suck in small quantities of air at any time.

Came across this re friction loss in corrugated pipes, the DN25 is nearest to the one above, a flow rate of 10LPM = 0.02M/M loss so the 5.8 coil should require 0.116M head. If the flow rate was 2 LPM (due to Thermosyphon) then the coil loss would only be 0.00464M and even allowing for the added pipeline losses there should be no reason IMO why the higher corrugated pipe losses should be a problem.
I read somewhere that clearing air from corrugated pipes requires a velocity of > 0.5 mps which will never be achieved with a gravity flow and this bore piping so hopefully your air purging etc will get rid of any air as the flow rate has to build from zero in this gravity system and any trapped air won't help.

Technical Information | Easyflex

www.easyflex.co.za

 

[Neville Hillyer]

Came across this re friction loss in corrugated pipes, the DN25 is nearest to the one above, a flow rate of 10LPM = 0.02M/M loss so the 5.8 coil should require 0.116M head. If the flow rate was 2 LPM (due to Thermosyphon) then the coil loss would only be 0.00464M and even allowing for the added pipeline losses there should be no reason IMO why the higher corrugated pipe losses should be a problem.
I read somewhere that clearing air from corrugated pipes requires a velocity of > 0.5 mps which will never be achieved with a gravity flow and this bore piping so hopefully your air purging etc will get rid of any air as the flow rate has to build from zero in this gravity system and any trapped air won't help.

Technical Information | Easyflex

www.easyflex.co.za

It would be helpful if you could find the reference for "clearing air from corrugated pipes requires a velocity of > 0.5 mps" especially as Telford advertise :

"Telford Stainless Vented Cylinders
Suitable replacement for copper vented
Telford Copper & Stainless Cylinders Ltd offer a stainless steel version of the conventional open-vented cylinder, traditionally made from copper. Made in the same production line and from the same material as our Unvented range, we can offer a cost effective alternative to copper vented cylinders that are manufactured to the same high standards as our unvented range."

The above words appear in their earlier publications but at the time of writing it is at the top of page 7 of the first download at: Telford Copper & Stainless Cylinders Brochure | Tristor, Tornado & Tempest Installation Guides - https://www.telford-group.com/downloads/general-downloads/

Before I placed my order I wrote to Telford and said: "I wish to replace a 20 year old 1200x450 Hercal hot water cylinder with the minimum of plumbing alterations." My initial email to Telford included a full specification and drawing of the cylinder I wished to replace.

They did warn me that most pipe connections would be in different locations to the Hercal but they did not warn me that they would supply a corrugated coil which would not self-clear air locks.

The delivered cylinder came with a 5 year printed guarantee and despite several protests they have still not replaced it with their widely advertised 10 year guarantee.

It is unfortunate that an established, well respected company, allowed this order to go so badly wrong and have done little, so far, to put it right.

 

[John.g]

Sorry Neville, but I just can't locate that link just now but it certainly stated a minimum velocity which I think was 0.5 mps so common sense would indicate that corrugated piping isn't compatible with large bore piping and low flow rates which are common to gravity flow systems, IMO.
Its strange that Telford can't/won't provide "evidence" of a cylinder similar to yours with a corrugated coil running on gravity circulation.

 

[Neville Hillyer]

Sorry Neville, but I just can't locate that link just now but it certainly stated a minimum velocity which I think was 0.5 mps so common sense would indicate that corrugated piping isn't compatible with large bore piping and low flow rates which are common to gravity flow systems, IMO.
Its strange that Telford can't/won't provide "evidence" of a cylinder similar to yours with a corrugated coil running on gravity circulation.

I have not asked Telford for this evidence. Mainly because some while ago I had unhelpful email exchanges with a senior member of the company so wish to be very sure of my grounds before I go back to him.

From information supplied here I am hopeful that I will be able to get it working but it may first need mains reverse flushing to remove air locks.

 

[John.g]

Spoke to Joule (Dublin) rep briefly and the technical Dept. informed him that they use 1 ins smooth bore coils in their gravity systems.

 

[Neville Hillyer]

Spoke to Joule (Dublin) rep briefly and the technical Dept. informed him that they use 1 ins smooth bore coils in their gravity systems.

Thanks for the useful information. Nice looking cylinders at joule.ie/knowledge-centre but they don't appear to do vented although this may not alter the gravity circulation criteria. Unvented is probably less likely to suck in air during normal use.

 

[Brambles]

One of our people fitted a Replacement Telford Indirect Vented cylinder (type G 9E) today in a three storey property in Oxford. This was a pumped system. However, looking at the literature and the instructions et al that came with the cylinder (delivered to us direct by Telford) - it is fitted with a 28mm inside diameter coil. From the chart ( which sets out the full standard vented Telford range (models 0 to 14 plus 9E)) in the instructions, There are only two models in the standard Telford range the 0 and 1 (96litre and 72 litre respectively) that are fitted with a 22mm inside diameter coil. It is stated in the notes that these cylinders are for pumped primary’s only.

All the cylinders in the Telford range for gravity circulation are shown as having either 28mm or 35mm id coils

 

[John.g]

"All the cylinders in the Telford range for gravity circulation are shown as having either 28mm or 35mm id coils"
Does it state/implicate corrugations or not?.

 

[Brambles]

All the cylinders in the Telford range for gravity circulation are shown as having either 28mm or 35mm id coils"
Does it state/implicate corrugations or not?.

No, copy appended below

 

[Chuck]

I am trying to compile a full list of possible reasons for the replacement cylinder not getting any heat. Here is my list so far:
[...]

7. Bathoom radiator loop providing a low impedance path in parallel with the cylinder coil.

Did you change the lockshield setting on that radiator at some point? If so, you might have left it too open.

Personally, I'd have fitted a circulating pump about a year ago. It doesn't take much to stop gravity circulation working and diagnosing the cause is often a waste of time because the remedy is mostly likely to be 'fit a circulating pump...' anyway.

 

[Neville Hillyer]

One of our people fitted a Replacement Telford Indirect Vented cylinder (type G 9E) today in a three storey property in Oxford. This was a pumped system. However, looking at the literature and the instructions et al that came with the cylinder (delivered to us direct by Telford) - it is fitted with a 28mm inside diameter coil. From the chart ( which sets out the full standard vented Telford range (models 0 to 14 plus 9E)) in the instructions, There are only two models in the standard Telford range the 0 and 1 (96litre and 72 litre respectively) that are fitted with a 22mm inside diameter coil. It is stated in the notes that these cylinders are for pumped primary’s only.

All the cylinders in the Telford range for gravity circulation are shown as having either 28mm or 35mm id coils

I am afraid I could not read your attachment. I have looked for the equivalent page on Telford's site and found the attached. It appears that the table is for copper and not stainless. I could see no mention of "internal diameter". I suspect 22mm and 28mm refer to the compression fitting sizes and not the pipe diameter. If you do have a readable page specifying an internal diameter of 28mm I would be interested to see it.

My problem relates to the cylinder supplied to me but nevertheless it would be interesting to see if there has been a move to larger pipe sizes.

I suspect that corrugated is the cheaper solution for stainless as a very thin wall will withstand quite high pressures and it is easily made into a coil. A plain copper coil is an established technology and may still be relatively inexpensive.
[automerge]1590231834[/automerge]

7. Bathoom radiator loop providing a low impedance path in parallel with the cylinder coil.

Did you change the lockshield setting on that radiator at some point? If so, you might have left it too open.

Personally, I'd have fitted a circulating pump about a year ago. It doesn't take much to stop gravity circulation working and diagnosing the cause is often a waste of time because the remedy is mostly likely to be 'fit a circulating pump...' anyway.

The coil gets zero heat with all settings of bathroom radiator valves including completely closed.

Gravity circulation has never been a problem for me with older central heating systems. It had worked, without any difficulty, in this property for about 50 years until I changed the traditional Hercal copper cylinder to a Telford stainless cylinder.

 

[EvilDrPorkChop]

Have the horizontal runs been checked after the new install? Is it possible the horizontal run could have been disturbed and pushed down under the floor causing a drop in the pipework rather than a steady rise. As I think other's have said the distance the gravity circs are run Horizontally seems quite large - however if it's worked for 50 years before must be OK
(And Bathroom rad works)

I had a very similar issue with my in Laws log burner and heat sink rad that was fitted by a previous installer. The rad would always work however the coil in the cylinder wouldn't - I concluded before ripping the thing out was that the circs to the cylinder didn't have great enough horizontal gains as the pipework was clear.

I've replaced old gravity cylinders with cylinders that are meant to be fully pumped before now (Due to what was needed and future upgrades coming) and never had any issues with them circulating on gravity systems.

What was the issue with the old cylinder? Did it leak or was a leak developed on the coil and CH & HW water was mixing?

 

[Neville Hillyer]

Have the horizontal runs been checked after the new install? Is it possible the horizontal run could have been disturbed and pushed down under the floor causing a drop in the pipework rather than a steady rise. As I think other's have said the distance the gravity circs are run Horizontally seems quite large - however if it's worked for 50 years before must be OK
(And Bathroom rad works)

I had a very similar issue with my in Laws log burner and heat sink rad that was fitted by a previous installer. The rad would always work however the coil in the cylinder wouldn't - I concluded before ripping the thing out was that the circs to the cylinder didn't have great enough horizontal gains as the pipework was clear.

I've replaced old gravity cylinders with cylinders that are meant to be fully pumped before now (Due to what was needed and future upgrades coming) and never had any issues with them circulating on gravity systems.

What was the issue with the old cylinder? Did it leak or was a leak developed on the coil and CH & HW water was mixing?

From the calculations in this thread it appears very unlikely that there is insufficient pressure around the circuit to promote gravity circulation. However removal of air locks is another matter. I am not aware of the pipes under the floor having moved very much but there could be less slope than before. The only practical way to examine this is to remove a portion of kitchen ceiling which I am reluctant to do unless all else fails.

Earlier cylinders only lasted about ten years but this last one was over 20 years old. They were all Hercal but the latest one had a sacrificial anode. The early ones leaked between primary and secondary but the last one developed a small hole at a weak point near the blanked immersion heater opening. This had been patched several times. Initially by Araldite and more recently by solder.

 

[Brambles]

Neville,

All the information is in the Telford 2019 technical product catalogue 40. If you cannot source a copy PM me and I will email you a PDF copy. I don’t think that I can post a PDF on this site (But may wrong on that).

 

[fixitflav]

I don’t think that I can post a PDF on this site (But may wrong on that).

You can, I've done it a few times.

 

[John.g]

Maybe zip it?? ( and it's a long long way to Tipperary,) 20 charc.

 

[fixitflav]

You can, I've done it a few times.

If you haven't already, you could try saving it on a drive, then click on the file name to attach it.

 

[Neville Hillyer]

Neville,

All the information is in the Telford 2019 technical product catalogue 40. If you cannot source a copy PM me and I will email you a PDF copy. I don’t think that I can post a PDF on this site (But may wrong on that).

I would be grateful if you could post the PDF to this site.

 

[Brambles]

Full Telford technical brochure as requested.

 

[Neville Hillyer]

One of our people fitted a Replacement Telford Indirect Vented cylinder (type G 9E) today in a three storey property in Oxford. This was a pumped system. However, looking at the literature and the instructions et al that came with the cylinder (delivered to us direct by Telford) - it is fitted with a 28mm inside diameter coil. From the chart ( which sets out the full standard vented Telford range (models 0 to 14 plus 9E)) in the instructions, There are only two models in the standard Telford range the 0 and 1 (96litre and 72 litre respectively) that are fitted with a 22mm inside diameter coil. It is stated in the notes that these cylinders are for pumped primary’s only.

All the cylinders in the Telford range for gravity circulation are shown as having either 28mm or 35mm id coils

Thanks for the PDF. Whilst you may be correct about the internal diameter I am unable to find any reference to 'internal diameter'. In the attached enlarged chart I can only see a column called 'Size of Primary Heater' which I am inclined to think are compression fitting sizes.

 

[Brambles]

“Size of the primary heater” is the Internal diameter of the coil in mm.

The connections on Telford vented cylinders are normally all the same - G1 which has a Nominal Bore of just under 30mm irrespective of the internal coil internal diameter.

in essence, you cannot determine the internal coil diameter from the external connection. Unless of course you have long thin fingers!

The external fittings are shown in the last two columns of the chart that you have posted

 

[Neville Hillyer]

“Size of the primary heater” is the Internal diameter of the coil in mm.

The connections on Telford vented cylinders are normally all the same - G1 which has a Nominal Bore of just under 30mm irrespective of the internal coil internal diameter.

in essence, you cannot determine the internal coil diameter from the external connection. Unless of course you have long thin fingers!

The external fittings are shown in the last two columns of the chart that you have posted

My understanding is that G is the German/ISO designation equivalent to BSPP. These were specified for thick steel gas pipes and so tend to be a size larger than copper. G1 was originally for a pipe with a 1 inch internal diameter.

Whilst I am not saying you are wrong, I continue to have two problems with this chart:

1 - it is for copper cylinders and not stainless
2 - internal coil diameter is not clearly stated.

 

[Brambles]

Neville,

I don’t think that there is any further help I can offer. I am sure that Telford will explain how your cylinder has been configured.

With respect to ISO G1 and G1/2 is a very common fitting in the UK.

 

[Gasmk1]

Don’t you think it is time to put this to bed gone on long enough.