Gas Leak Quantity

I had a major domestic crisis last week, when the bod who came to replace my gas meter condemned my pipes as too leaky. Soon resolved by a local fitter who replaced the sixty-odd year old iron pipes with new copper ones.

This left me wondering how much gas had been escaping. I forget the numbers but the manometer was dropping at about twice the allowed rate. Has anyone got any idea how this would relate to cubic feet, roughly? Obviously we're talking an order-of-magnitude guess here.

My gut feeling is that the loss was negligible, probably a lot less than the gas used by a pilot light, and so I won't be noticing any reduction in my bills.

Reply to
Phil
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Reply to
Ericp

If enough gas were escaping that it would register on your bills you and your neighbours would likely not be around to care about it :-|

Reply to
John Stumbles

You can't really extrapolate a quantity of gas lost based on just a rate of fall in pressure - without also knowing the total volume of gas contained in the all the pipework. Needless to say - the smaller the volume of gas contained the more pronounced the effects of any given leak will be.

Reply to
John Rumm

That's what I thought. (-:

Reply to
Phil

Indeed. That's why I said I was hoping someone might be able to come up with a rough order-of-magnitude estimate.

Reply to
Phil

An unaccpetable leak would be something like an unlit pilot light. Maybe

20pence a day? Maybe more.

Alan.

Reply to
A.Lee

Well I spose one could make a guesstimate...

Say the system has a total equivalent volume of 30m of 15mm pipe, that would equate to length x area or 30 x (3.14 x (0.0075)^2) = 0.005 m^3

So lets say it starts your two minute test period at an absolute pressure of 1020 mbar, and drops twice the allowed[1] 4 mbar in the time, giving a final pressure of 1012.

We will assume the temperature remains constant, and so can assume Boyle's Law applies and that P1V1 = P2V2, giving 1020 x 0.005 = 1012 x V2, or V2 = 1020 x 0.005 / 1012 = 0.00504, or an escape of P2 - P1 =

0.00004 m^3 of gas in 2 mins, or 0.0012 m^3 / hour.

That's about 10.5m^3 per year, or 370 cu ft. About what a 35kW boiler could get through in 11 hours or so.

So all in all less than a fivers worth of gas per year - quite possibly less than a quid.

[1] Allowed with appliances connected, without there is no allowed drop.
Reply to
John Rumm

Many thanks for that. My school physics was just too long ago. So - as expected - no cash bonus!

Thanks to everyone else for their contributions as well.

Reply to
Phil

Duh! make that V2 - V1 ;-)

Nope, I think like John S said - if its costing you enough to worry about, then the cost it the least of your worries!

Reply to
John Rumm

In message , harry writes

Same with filling station pumps, and deliveries of central hearing oil.

I expect that petrol/diesel, being stored underground, remains at a reasonably constant temperature, summer and winter, and never has time to warm up or cool down while it is being delivered to your vehicle fuel tank.

However, CH oil, coming out of a tanker driving all day around the countryside, could vary a lot in temperature by the time it is delivered to you. Presumably, in the depth of winter, and the oil will be contracted when you get it, you get more calories for your money. On the other hand, in the depth of winter, CH oil prices are often higher than in the summer. I suppose it's a swings-and-roundabout situation.

Reply to
Ian Jackson

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Reply to
jgharston

That's not a leak, it's an unfinished T-junction!

Reply to
PeterC

That's sort of been on my mind for a while but I don't think the chnage is particulary significant. Our tank sits in full sun during the day so gets "quite warm" I take weekly level readings to get a rough prediction as to when we will need some more. I can't say I've noticed that the level goes up or falls less slowly than expected in long hot periods of weather.

With curisoity peaqued wanders off to google. Kerosene has an coeffcient of expansion of 0.00099/k. So for 2000l and say 40 K temp range that is 2000 * 0.00099 * 40 =3D 79.2l at 60p/l =3D =A347.52 hum...=

But I very much doubt that the delivery temperature of our oil varies by 40K. It might from the coldest part of winter to the hottest summer vary 20K but that's still 40l in a 2000l delivery. I shall have to ask them if their meter is oil temperature compenstated.

Reply to
Dave Liquorice

Very little monetary cost because of the smell - even a small sized leak has a "disproportionate" smell to it which even if above head height will be noticeable in the general area enough times in a year to get noticed.

Iron pipes can really catch you out re corrosion. Lead and block tin can be perfectly serviceable if they have copper/brass fittings at each end, but are subject to crystalline fracture particularly if festooned on cramps spaced too far apart or corrosion related failure surprisingly if run by black mortar (sulphuric acid) by leaking gutter (over years). That last one caught a long gone relative in 1984 when a slight smell on removing blown plaster browning became a full blast. Gas pressure is relatively low, so you have have a "net curtain" which can become a full bore leak. Likewise lead & iron in floors can rot just below the surface under stairs. This caught out ICL in ?scotland? where seemingly ok pipework was net-curtains and small leaks became sudden full bore leaks.

Best pipework is 1 piece copper plastic coated where necessary or tracpipe, although tracpipe can introduce more joints and is more costly. Soldering skill is highly variable these days with flux left in place and solder trails like ancient candles. Compression joints are permitted with gas (Tracpipe) but absolutely must be accessible - the interpretation of which is usually lax on the day, tight on any subsequent inspection :-)

Reply to
js.b1

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