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UK diy (uk.d-i-y) For the discussion of all topics related to diy (do-it-yourself) in the UK. All levels of experience and proficency are welcome to join in to ask questions or offer solutions. |
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#1
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I was recently told when a plumber cut off a dead leg in our gas pipework
that we had a small (but allowable) leak in our system. Clearly he wasn't wild about chasing the leak but I'd rather there wasn't one. Before I start hunting, what's the acceptable leak level in mbar/min? Tim |
#2
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In an earlier contribution to this discussion,
Tim Downie wrote: I was recently told when a plumber cut off a dead leg in our gas pipework that we had a small (but allowable) leak in our system. Clearly he wasn't wild about chasing the leak but I'd rather there wasn't one. Before I start hunting, what's the acceptable leak level in mbar/min? Tim I don't know the answer, but is that the only way to measure leaks - in mbar/min? If so, surely that makes the max permissible *absolute* leak rate (gms/min, or whatever) a function of the volume of your pipework. Is that's what's intended? -- Cheers, Roger ______ Email address maintained for newsgroup use only, and not regularly monitored.. Messages sent to it may not be read for several weeks. PLEASE REPLY TO NEWSGROUP! |
#3
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On Tue, 05 Feb 2008 12:33:24 +0000, Tim Downie wrote:
I was recently told when a plumber cut off a dead leg in our gas pipework that we had a small (but allowable) leak in our system. Clearly he wasn't wild about chasing the leak but I'd rather there wasn't one. Before I start hunting, what's the acceptable leak level in mbar/min? For pipework it's no observable drop, which IIRC is stated somewhere to be less than 0.25mbar (over 2 minutes test). If any appliance is connected then it depends on the type (and volume) of the gas meter, but if your CORGI registered installer is testing that his pipework is sound he should shut off appliances so that he's testing only the pipework. If he's canny he'll have tested the installation before he made any changes in which case if there was a slight but acceptable drop beforehand *and no smell of gas* and the drop is no greater afterwards he can probably put it down to appliance drop and leave it like that. -- John Stumbles What is a simile like? |
#4
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John Stumbles wrote:
On Tue, 05 Feb 2008 12:33:24 +0000, Tim Downie wrote: I was recently told when a plumber cut off a dead leg in our gas pipework that we had a small (but allowable) leak in our system. Clearly he wasn't wild about chasing the leak but I'd rather there wasn't one. Before I start hunting, what's the acceptable leak level in mbar/min? For pipework it's no observable drop, which IIRC is stated somewhere to be less than 0.25mbar (over 2 minutes test). If any appliance is connected then it depends on the type (and volume) of the gas meter, but if your CORGI registered installer is testing that his pipework is sound he should shut off appliances so that he's testing only the pipework. It wasn't so long ago that a gas fitter came and did the old "sucking of teeth" bit when he saw our gas cooker didn't have an isolating valve (which he then fitted). It took us some time to realise that the odd smell in the kitchen was coming from the back of the unit where he had fitted the valve, which was leaking. ;-) Fortunately, it just took a bit of working the valve open & closed a few times to get it to seal properly but it's made me a wee bit sceptical about the benefits of all these valves. If he's canny he'll have tested the installation before he made any changes in which case if there was a slight but acceptable drop beforehand *and no smell of gas* and the drop is no greater afterwards he can probably put it down to appliance drop and leave it like that. We don't have a smell of gas (unlike the time another BG engineer who supposedly had tested our system cocked up) but I've decided to invest in a manometer to see if I can isolate the leak. On several occasions, I have heard mention (from plumbers) of a figure (something like 4mm or 4mbar over some period or other mentioned), hence my question. Tim |
#5
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John Stumbles wrote:
On Tue, 05 Feb 2008 12:33:24 +0000, Tim Downie wrote: I was recently told when a plumber cut off a dead leg in our gas pipework that we had a small (but allowable) leak in our system. Clearly he wasn't wild about chasing the leak but I'd rather there wasn't one. Before I start hunting, what's the acceptable leak level in mbar/min? For pipework it's no observable drop, which IIRC is stated somewhere to be less than 0.25mbar (over 2 minutes test). Just tested the system "appliances isolated" and the good news is that there's no drop. Still no drop with CH boiler connected. A small drop (0.5mbar over 2 minutes) with the cooker & tumble dryer connected. I rather suspect that these bayonet connections account for most of the leak. With that pressure drop (& no smell of gas) should I stop worrying? Tim |
#6
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On Tue, 5 Feb 2008 13:41:30 -0000, "Tim Downie"
wrote: John Stumbles wrote: On Tue, 05 Feb 2008 12:33:24 +0000, Tim Downie wrote: I was recently told when a plumber cut off a dead leg in our gas pipework that we had a small (but allowable) leak in our system. Clearly he wasn't wild about chasing the leak but I'd rather there wasn't one. Before I start hunting, what's the acceptable leak level in mbar/min? For pipework it's no observable drop, which IIRC is stated somewhere to be less than 0.25mbar (over 2 minutes test). Just tested the system "appliances isolated" and the good news is that there's no drop. Still no drop with CH boiler connected. A small drop (0.5mbar over 2 minutes) with the cooker & tumble dryer connected. A gas tumble dryer ?? |
#7
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#8
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#9
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On Tue, 05 Feb 2008 12:49:28 +0000, Roger Mills wrote:
In an earlier contribution to this discussion, Tim Downie wrote: I was recently told when a plumber cut off a dead leg in our gas pipework that we had a small (but allowable) leak in our system. Clearly he wasn't wild about chasing the leak but I'd rather there wasn't one. Before I start hunting, what's the acceptable leak level in mbar/min? Tim I don't know the answer, but is that the only way to measure leaks - in mbar/min? If so, surely that makes the max permissible *absolute* leak rate (gms/min, or whatever) a function of the volume of your pipework. Is that's what's intended? Since the volume of the pipework+meter is to a first approximation is similar for all ordinary domestic installations, then the pressure drop and time equates to roughly similar amount of gas leakage. If you reckoned that the volume of the pipe+meter is about 10 litres then 4 mbar/2min is about 20cm^3 per min. That's about about 1/2 an egg cup per min, MAXIMUM when the old appliances are connected and there is NO SMELL of gas. If you have a smaller electronic meter (E6 type) or heavy domestic/light commercial (R5) type then the times and pressures are different. On large domestic installations and above then calculations are required to work out the permitted leakage limits. THE PERMITTED LEAKAGE FOR PIPEWORK (new or old) IS ZERO. I.e. less than 0.25mbar/2min on a normal installation. That's less than 1cm^3 per min. -- Ed Sirett - Property maintainer and registered gas fitter. The FAQ for uk.diy is at http://www.diyfaq.org.uk Gas fitting FAQ http://www.makewrite.demon.co.uk/GasFitting.html Sealed CH FAQ http://www.makewrite.demon.co.uk/SealedCH.html Choosing a Boiler FAQ http://www.makewrite.demon.co.uk/BoilerChoice.html |
#11
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The message
from "Tim Downie" contains these words: We don't have a smell of gas (unlike the time another BG engineer who supposedly had tested our system cocked up) but I've decided to invest in a manometer to see if I can isolate the leak. What sort and where from? I am currently on the lookout for a cheap manometer but so far all I have found are expensive digital types. Having written the above I thought I had better do another more specific search and while I found a number of U tube manometers some were expensive and it was by no means clear that the cheaper ones could be used to check for gas soundness. Any pointers would be appreciated (and no I don't want to make one from scratch). -- Roger Chapman |
#12
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On Tue, 5 Feb 2008 16:27:25 GMT, Roger
wrote: The message from "Tim Downie" contains these words: We don't have a smell of gas (unlike the time another BG engineer who supposedly had tested our system cocked up) but I've decided to invest in a manometer to see if I can isolate the leak. What sort and where from? I am currently on the lookout for a cheap manometer but so far all I have found are expensive digital types. Having written the above I thought I had better do another more specific search and while I found a number of U tube manometers some were expensive and it was by no means clear that the cheaper ones could be used to check for gas soundness. Any pointers would be appreciated (and no I don't want to make one from scratch). B&Q - about 15 quid. -- Frank Erskine |
#13
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Roger wrote:
The message from "Tim Downie" contains these words: We don't have a smell of gas (unlike the time another BG engineer who supposedly had tested our system cocked up) but I've decided to invest in a manometer to see if I can isolate the leak. What sort and where from? A Monument one like this one. http://www.amazon.co.uk/gp/product/B...F8&me=&seller= I got mine in B&Q (same price) but if you get one there, make very sure that the rubber connecting tube in in the pack with it. Two out of the three in stock in my local store were missing their tubes. (Light fingered plumbers I guess). Tim |
#14
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Ed Sirett wrote:
THE PERMITTED LEAKAGE FOR PIPEWORK (new or old) IS ZERO. I.e. less than 0.25mbar/2min on a normal installation. So 0.24mbar/2min is okay? ;-) As it happens, my pipework seems fine and since redoing my dryer connection, my "appliance leak" seems to have gone too. Thanks for the info. Tim |
#15
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In an earlier contribution to this discussion,
Roger wrote: I am currently on the lookout for a cheap manometer but so far all I have found are expensive digital types. Any pointers would be appreciated (and no I don't want to make one from scratch). Why ever not? This *is* uk-d-i-y! I made one years ago by bending some clear plastic tube into e U shape, and fixing it onto a piece of floorboard, with a sheet of graph paper behind it. I think I've still got it somehere! -- Cheers, Roger ______ Email address maintained for newsgroup use only, and not regularly monitored.. Messages sent to it may not be read for several weeks. PLEASE REPLY TO NEWSGROUP! |
#16
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It happens that Roger formulated :
The message from "Tim Downie" contains these words: We don't have a smell of gas (unlike the time another BG engineer who supposedly had tested our system cocked up) but I've decided to invest in a manometer to see if I can isolate the leak. What sort and where from? I am currently on the lookout for a cheap manometer but so far all I have found are expensive digital types. Having written the above I thought I had better do another more specific search and while I found a number of U tube manometers some were expensive and it was by no means clear that the cheaper ones could be used to check for gas soundness. Any pointers would be appreciated (and no I don't want to make one from scratch). You only need a bit of clear plastic tube formed into a U shape, clipped to a bit of wood and filled with water. -- Regards, Harry (M1BYT) (L) http://www.ukradioamateur.co.uk |
#17
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The message
from "Tim Downie" contains these words: What sort and where from? A Monument one like this one. http://www.amazon.co.uk/gp/product/B...F8&me=&seller= 30 mbar. I got mine in B&Q (same price) but if you get one there, make very sure that the rubber connecting tube in in the pack with it. Two out of the three in stock in my local store were missing their tubes. (Light fingered plumbers I guess). Thanks Tim and Frank. I think I must be going senile. I had managed to get it into my head that the domestic gas pressure was 80 mbar, not 20 mbar. -- Roger Chapman |
#18
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The message
from "Roger Mills" contains these words: Any pointers would be appreciated (and no I don't want to make one from scratch). Why ever not? This *is* uk-d-i-y! Because I have too many other tuits of the round sort and if I have to go shopping for the tubing I might just as well get the finished article. -- Roger Chapman |
#19
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On Tue, 05 Feb 2008 16:27:25 +0000, Roger wrote:
I am currently on the lookout for a cheap manometer but so far all I have found are expensive digital types. Having written the above I thought I had better do another more specific search and while I found a number of U tube manometers some were expensive and it was by no means clear that the cheaper ones could be used to check for gas soundness. You really only need a length of winemaking tube folded into a U shape taped alongside a ruler. 1" is one inch water gauge: 30' of water is 1 bar: the rest is arithmetic. Any pointers would be appreciated (and no I don't want to make one from scratch). OK then, BES do a U-tube type for about a tenner (pipe not included: they do black rubber pipe for NG separately). It's useful to find a bit of larger diameter pipe whick fits snugly over the non-manometer end of the tube to fit onto meter test nipples which are too big to get the regular diameter tube over. I've got a very nice bit which was once the boot that went over the spark plug from an ignition lead. While you're ordering from BES get some of their flourescent dye to put in the water in the u-tube. Or you can use a minute dab of food colour, though prolonged use is likely to leave a precipitate on the inside of the tube making it harder to read. I gather there's a website somewhere all about u-tubes. :^| -- John Stumbles A: Because it messes up the order in which people read text. Q: Why is top-posting a bad thing? |
#21
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![]() "Tim Downie" wrote in message ... I was recently told when a plumber cut off a dead leg in our gas pipework that we had a small (but allowable) leak in our system. Clearly he wasn't wild about chasing the leak but I'd rather there wasn't one. Before I start hunting, what's the acceptable leak level in mbar/min? Zero! Unless you know the gas is being vented to the outside air how do you know it will not go *BANG*? It may take weeks or months to build to an explosive mixture but how do you know it hasn't? |
#22
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![]() "Roger" wrote in message k... The message from "Tim Downie" contains these words: We don't have a smell of gas (unlike the time another BG engineer who supposedly had tested our system cocked up) but I've decided to invest in a manometer to see if I can isolate the leak. What sort and where from? I am currently on the lookout for a cheap manometer but so far all I have found are expensive digital types. Having written the above I thought I had better do another more specific search and while I found a number of U tube manometers some were expensive and it was by no means clear that the cheaper ones could be used to check for gas soundness. Any pointers would be appreciated (and no I don't want to make one from scratch). A piece of wood, some staples and a plastic tube too DIY? ;-) |
#23
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![]() "dennis@home" wrote in message ... "Tim Downie" wrote in message ... I was recently told when a plumber cut off a dead leg in our gas pipework that we had a small (but allowable) leak in our system. Clearly he wasn't wild about chasing the leak but I'd rather there wasn't one. Before I start hunting, what's the acceptable leak level in mbar/min? Zero! No such thing as zero. That would mean waiting infinitely long to prove that there was no leak. Unless you know the gas is being vented to the outside air how do you know it will not go *BANG*? Funnily enough, I have a nose. It's proved a lot more reliable than BG gas fitter's testing proceedures. It may take weeks or months to build to an explosive mixture but how do you know it hasn't? If we were talking about LPG, I would worry more but natural gas has a lower density than air, so it's less inclined to lurk. Tim |
#24
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On Tue, 05 Feb 2008 17:23:27 +0000, Tim Downie wrote:
Ed Sirett wrote: THE PERMITTED LEAKAGE FOR PIPEWORK (new or old) IS ZERO. I.e. less than 0.25mbar/2min on a normal installation. So 0.24mbar/2min is okay? ;-) As it happens, my pipework seems fine and since redoing my dryer connection, my "appliance leak" seems to have gone too. Thanks for the info. Tim The 0.25 mbar is a way of saying no detectable drop. You could probably observe a smaller drop than that, but even holding the gas pipe with a warm hand can put 0.5 mbar or more onto the gauge. When using an electronic manometer they are very very sensitive and the last digit is 0.01 mbar i.e. Pascals i.e next to nothing. The digits will move around all the while when testing. -- Ed Sirett - Property maintainer and registered gas fitter. The FAQ for uk.diy is at http://www.diyfaq.org.uk Gas fitting FAQ http://www.makewrite.demon.co.uk/GasFitting.html Sealed CH FAQ http://www.makewrite.demon.co.uk/SealedCH.html Choosing a Boiler FAQ http://www.makewrite.demon.co.uk/BoilerChoice.html |
#25
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![]() "Tim Downie" wrote in message ... "dennis@home" wrote in message ... "Tim Downie" wrote in message ... I was recently told when a plumber cut off a dead leg in our gas pipework that we had a small (but allowable) leak in our system. Clearly he wasn't wild about chasing the leak but I'd rather there wasn't one. Before I start hunting, what's the acceptable leak level in mbar/min? Zero! No such thing as zero. That would mean waiting infinitely long to prove that there was no leak. Unless you know the gas is being vented to the outside air how do you know it will not go *BANG*? Funnily enough, I have a nose. It's proved a lot more reliable than BG gas fitter's testing proceedures. Well there is your first error.. to smell it means it has to be escaping into the room, what about the roof/floor/wall spaces where you don't stick your nose. It may take weeks or months to build to an explosive mixture but how do you know it hasn't? If we were talking about LPG, I would worry more but natural gas has a lower density than air, so it's less inclined to lurk. Checked your roof space recently? ;-) LPG is very dangerous on boats as they tend to be gas tight and there have been some very big bangs. Like I said any leak is dangerous unless you know where it is going. |
#26
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In message , "dennis@home"
writes If we were talking about LPG, I would worry more but natural gas has a lower density than air, so it's less inclined to lurk. Checked your roof space recently? ;-) LPG is very dangerous on boats as they tend to be gas tight and there have been some very big bangs. We were holidaying on a boat on the Norfolk Broads a few years back when the cooker stopped working. Boatyard sent someone out to fix it and we carried on... until I realised the inside was increasingly smelling of rotten cabbage. Very fast mooring and evacuation followed. The boatyard offered us compensation without us asking. ![]() -- Si |
#27
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dennis@home wrote:
"Tim Downie" wrote in message ... "dennis@home" wrote in message ... "Tim Downie" wrote in message ... I was recently told when a plumber cut off a dead leg in our gas pipework that we had a small (but allowable) leak in our system. Clearly he wasn't wild about chasing the leak but I'd rather there wasn't one. Before I start hunting, what's the acceptable leak level in mbar/min? Zero! No such thing as zero. That would mean waiting infinitely long to prove that there was no leak. Unless you know the gas is being vented to the outside air how do you know it will not go *BANG*? Funnily enough, I have a nose. It's proved a lot more reliable than BG gas fitter's testing proceedures. Well there is your first error.. to smell it means it has to be escaping into the room, what about the roof/floor/wall spaces where you don't stick your nose. Actually, I *do* stick my nose under the floor and into the loft. Haven't got any joints in my wall cavities. It may take weeks or months to build to an explosive mixture but how do you know it hasn't? If we were talking about LPG, I would worry more but natural gas has a lower density than air, so it's less inclined to lurk. Checked your roof space recently? ;-) See above. LPG is very dangerous on boats as they tend to be gas tight and there have been some very big bangs. Why are you telling me something I already know? I'm trying to make the point that a lighter than air gas is most unlikely to "take weeks or months" to build to an explosive mixture in a typically ventilated house. I'll wager that every gas induced house explosion with natural gas has been due to an accummulation *much* faster than "weeks or months". Like I said any leak is dangerous unless you know where it is going. Leak tested your own pipework and appliances lately? Or do you trust someone who's in a hurry and *doesn't* live in the same property as he/she is testing? Tim |
#28
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The message
from "dennis@home" contains these words: Any pointers would be appreciated (and no I don't want to make one from scratch). A piece of wood, some staples and a plastic tube too DIY? ;-) Life is too short to do everything. -- Roger Chapman |
#29
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In message , Huge
writes On 2008-02-06, Si $3o&m wrote: We were holidaying on a boat on the Norfolk Broads a few years back when the cooker stopped working. Boatyard sent someone out to fix it and we carried on... until I realised the inside was increasingly smelling of rotten cabbage. Yes, but Norfolk smnells like that. This was definitely not NfN -- Si |
#30
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![]() "Si" $3o&m wrote in message ... In message , "dennis@home" writes If we were talking about LPG, I would worry more but natural gas has a lower density than air, so it's less inclined to lurk. Checked your roof space recently? ;-) LPG is very dangerous on boats as they tend to be gas tight and there have been some very big bangs. We were holidaying on a boat on the Norfolk Broads a few years back when the cooker stopped working. Boatyard sent someone out to fix it and we carried on... until I realised the inside was increasingly smelling of rotten cabbage. Very fast mooring and evacuation followed. The boatyard offered us compensation without us asking. ![]() Serious question, why can't you get bottled natural gas specifically for use on boats? Given that boat makers can't use the ideal solution (i.e. drill holes in the bottom to let the gas out), it would seem immensely sensible to use a lighter than air gas on board boats. Tim -- Si |
#31
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On Thu, 07 Feb 2008 17:11:09 +0000, Tim Downie wrote:
Serious question, why can't you get bottled natural gas specifically for use on boats? Given that boat makers can't use the ideal solution (i.e. drill holes in the bottom to let the gas out), it would seem immensely sensible to use a lighter than air gas on board boats. Because natural gas can't be liquefied (at room temps & acheivable pressures) -- John Stumbles 87.5% of statistics are made up |
#32
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Tim Downie wrote:
snip Serious question, why can't you get bottled natural gas specifically for use on boats? Given that boat makers can't use the ideal solution (i.e. drill holes in the bottom to let the gas out), it would seem immensely sensible to use a lighter than air gas on board boats. Didn't I hear that the Hindenburg started out as a boat... ?? -- Rod |
#33
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John Stumbles wrote:
On Thu, 07 Feb 2008 17:11:09 +0000, Tim Downie wrote: Serious question, why can't you get bottled natural gas specifically for use on boats? Given that boat makers can't use the ideal solution (i.e. drill holes in the bottom to let the gas out), it would seem immensely sensible to use a lighter than air gas on board boats. Because natural gas can't be liquefied (at room temps & acheivable pressures) Darn! Knew there had to be a good reason. ;-) Tim |
#34
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![]() "Rod" wrote in message ... Tim Downie wrote: snip Serious question, why can't you get bottled natural gas specifically for use on boats? Given that boat makers can't use the ideal solution (i.e. drill holes in the bottom to let the gas out), it would seem immensely sensible to use a lighter than air gas on board boats. Didn't I hear that the Hindenburg started out as a boat... ?? It was a ship! |
#35
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On Thu, 07 Feb 2008 18:05:41 +0000, Tim Downie wrote:
Because natural gas can't be liquefied (at room temps & acheivable pressures) Darn! Knew there had to be a good reason. ;-) Actually it can be stored compressed, but it need sto be in the sort of bottles used for other compressed gases such as oxygen, nitrogen, CO2 etc. If you've come across these in a welding shop, science lab or hospital etc you'll know they are firkling *heavy*. However I recall seeing cars fitted with compressed methane bottles on roofracks in Ancona, Italy, in 1977. It was some sort of renewable scheme. Evidently didn't catch on. -- John Stumbles Pessimists are never disappointed |
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