Our under stairs cupboard smells of gas. There is a "dead leg" of the old
2" iron gas main in the cupboard capped with a lump of putty. (The gas has
been re-routed when the meter was moved outside and the street mains
replaced with plastic pipe).

If I put a plastic bag over the pipe, it slowly fills with smelly gas
(though not as smelly as neat gas). This gas does *not* burn however (I've
tried).

It seems this pipe is definitely the source of the smell (rest of system
recently tested and okay) but I'm puzzled as to what is coming through this
pipe.

Any thoughts?

Tim

"Tim Downie" wrote in message
...
Our under stairs cupboard smells of gas. There is a "dead leg" of the old
2" iron gas main in the cupboard capped with a lump of putty. (The gas
has been re-routed when the meter was moved outside and the street mains
replaced with plastic pipe).

If I put a plastic bag over the pipe, it slowly fills with smelly gas
(though not as smelly as neat gas). This gas does *not* burn however
(I've tried).

It seems this pipe is definitely the source of the smell (rest of system
recently tested and okay) but I'm puzzled as to what is coming through
this pipe.

Any thoughts?

Tim




It is probably a built up of the odorant put into the gas that is in the
pipe. Natural gas has no smell, mercaptan is added so people report gas
leaks.


mark

It *could* be gas leaking from elsewhere that is tracking through the
disused pipework.

A BG employee friend told me that (in the most serious cases) this is
one possible route to gas explosions - a leak from the under street
main, tracks through disused sewage pipes or whatever, until it finds
somewhere to form a pocket.

In your case, it may be nothing. Personally, I'd get an expert opinion.

Tim Downie wrote:
Our under stairs cupboard smells of gas. There is a "dead leg" of
the old 2" iron gas main in the cupboard capped with a lump of putty.
(The gas has been re-routed when the meter was moved outside and the
street mains replaced with plastic pipe).

If I put a plastic bag over the pipe, it slowly fills with smelly gas
(though not as smelly as neat gas). This gas does *not* burn however
(I've tried).

It seems this pipe is definitely the source of the smell (rest of
system recently tested and okay) but I'm puzzled as to what is coming
through this pipe.

Any thoughts?

Tim

If you report it, it's likely to cost you money.
If it were mine I would simply pour wet cement down it, filling it to about
150mm from the top, and then a few days later a tube of silicone sealant up
to the top of the pipe.
It's unlikely to be gas of any kind, and as one of the others have said,
it's possibly something drifting along the pipe from somewhere else, maybe
sewer gas, or a mixture of sewer odours and natural gas, or even coal gas,
either way, block it up.

"Phil L" wrote in message
.uk...
Tim Downie wrote:
Our under stairs cupboard smells of gas. There is a "dead leg" of
the old 2" iron gas main in the cupboard capped with a lump of putty.
(The gas has been re-routed when the meter was moved outside and the
street mains replaced with plastic pipe).

If I put a plastic bag over the pipe, it slowly fills with smelly gas
(though not as smelly as neat gas). This gas does *not* burn however
(I've tried).

It seems this pipe is definitely the source of the smell (rest of
system recently tested and okay) but I'm puzzled as to what is coming
through this pipe.

Any thoughts?

Tim

If you report it, it's likely to cost you money.
If it were mine I would simply pour wet cement down it, filling it to
about 150mm from the top, and then a few days later a tube of silicone
sealant up to the top of the pipe.
It's unlikely to be gas of any kind, and as one of the others have said,
it's possibly something drifting along the pipe from somewhere else, maybe
sewer gas, or a mixture of sewer odours and natural gas, or even coal gas,
either way, block it up.

Thanks, I'm inclined to agree. I'm satisfied that it's not flammable and I
think the smell is down to residue in the old gas pipe. I suspect the flow
through the pipe was induced by the winds yesterday (and the fact that we
have an open chimney). creating a slightly negative pressure in the house.

Tim

Phil L wrote:
Tim Downie wrote:
Our under stairs cupboard smells of gas. There is a "dead leg" of
the old 2" iron gas main in the cupboard capped with a lump of putty.
(The gas has been re-routed when the meter was moved outside and the
street mains replaced with plastic pipe).

If I put a plastic bag over the pipe, it slowly fills with smelly gas
(though not as smelly as neat gas). This gas does *not* burn however
(I've tried).

Out of curiosity have you taken a bag of neat gas and tried to ignite it in
the same way as a control. i.e can you easily burn a similar size sample of
mains gas? I've no idea how easy this is. But I'd use a long taper just in
case.


It seems this pipe is definitely the source of the smell (rest of
system recently tested and okay) but I'm puzzled as to what is coming
through this pipe.

Any thoughts?

Tim

If you report it, it's likely to cost you money.
If it were mine I would simply pour wet cement down it, filling it to about
150mm from the top, and then a few days later a tube of silicone sealant up
to the top of the pipe.
It's unlikely to be gas of any kind,

Well I'd tend to think that it is obviously a gas of one kind or another.

and as one of the others have said,
it's possibly something drifting along the pipe from somewhere else, maybe
sewer gas, or a mixture of sewer odours and natural gas, or even coal gas,
either way, block it up.


If it is sewer gas it could well be a problem.

Is the smell the same as that of the odourant in mains gas or is it more
like rotten eggs?

If it mildy resembles rotten eggs then there could be some hydrogen sulphide
present... often found in sewer gas. This can be a major problem.

You will smell it in low concentration 10-20 ppm but above about 90-100 ppm
it dulls/kills your olafactory sensors and you no longer register it. Only a
little above this level and you can lose conciousness and in the 1000 ppm
region it is fatal.

Of course it may just be a dead leg from trapped mains as you say.

If it is a mains gas smell then I would still report it to Transco. It is
very unlikely to cost you anything IMO and given a couple of tragic
incidents over the years they do like to respond and investigate these issues.

cheers

David

If it is a mains gas smell then I would still report it to Transco. It is
very unlikely to cost you anything IMO and given a couple of tragic
incidents over the years they do like to respond and investigate these issues.

I would agree, twice when I have reported a potential leak to Transco,
they have turned up very quickly and investigated. The first time,
they ended up replacing the pipe into our house and it took all of one
Sunday evening and they didn't leave until about 1am.

Second time they tracked it to a loose connection from the meter.

In neither case was there any charge. I think they have some sort of
statuatory obligation to investigate this.

On Tue, 22 Jan 2008 04:25:59 -0800 (PST) someone who may be Tim
Decker wrote this:-

In neither case was there any charge. I think they have some sort of
statuatory obligation to investigate this.

If I have kept up to date the system operator does, free of charge
for householders.

In the usual fashion, Transco no longer exist. If
http://www.nationalgrid.com/uk/About/history/ is up to date they are
partly now National Grid Gas plc. However, if the house is in
"Scotland, the North East, Wales & West and the South of England"
there is another organisation which does the same thing.

Here it is Scotland Gas Networks, a company held by Scotia Gas
Networks http://www.scotiagasnetworks.co.uk

More work for lawyers with little or no benefit to "the real world",
no-doubt.



--
David Hansen, Edinburgh
I will *always* explain revoked encryption keys, unless RIP prevents me
http://www.opsi.gov.uk/acts/acts2000/00023--e.htm#54

....snip...
Out of curiosity have you taken a bag of neat gas and tried to ignite it
in the same way as a control. i.e can you easily burn a similar size
sample of mains gas? I've no idea how easy this is. But I'd use a long
taper just in case.

I seem to remember that one of the original proponents of gas, when faced
with criticism because poor installations (dodgy installers using second
hand gun barrels taped together if memory serves) were exploding, gave a
demostration whereby he strode over to a gasometer, put a pickaxe through it
and then proceeded to apply a match. A large yellow flame resulted but not
the explosion expected by the observers.

Gas on its own doesn't burn dramatically, only when you mix it with air (for
example leaving it to mix with the air under stairs!) so it is quite
possible that a "bag full of gas" might not actually do much at all.

Paul DS

Paul D.Smith wrote:


Gas on its own doesn't burn dramatically, only when you mix it with
air (for example leaving it to mix with the air under stairs!) so it
is quite possible that a "bag full of gas" might not actually do much
at all.

Which is why I connected it to a small bit of tubing and then "squirted" the
gas slowly in the direction of an open flame. At slow gas speeds nothing
happened. At higher speeds, it blew the flames out on my gas cooker! I'm
happy it's not flammable. Air filtering through the ground and picking up
residue from the stenching agent in the old iron pipework seems the
likeliest explanation.

Given that the last gas leak we had in our house was *caused* by BG monkeys,
I'm not in too much of a hurry to let them in again.

Tim

In article ,
DM wrote:

If it is a mains gas smell then I would still report it to Transco. It is
very unlikely to cost you anything IMO and given a couple of tragic
incidents over the years they do like to respond and investigate these issues.

If you are going to report it, a word of advice ... DO NOT report it in
the late afternoon/evening!

There had been a smell of gas round our way for some time - weeks,
not all the time, just the occasional whiff... Got our friendly local
plumber in to check our own house pipe works and it was as sound as a
sound thing, so foolishly called the number ...

After pretending to shut down our own gas, and going through the script
with the phone driod, an engineer was summoned. This was at about 6pm.

I explained the situation, that we get the occasional whiff of gas in
one corner of the room, and very occasionally outside in the street. He
checked our own piping and was happy it wasn't ours..

There then followed many hours of to-ing & fro-in )-: He went round with
the sniffer, inside and outside, to our neighbours and back again, then
started punching holes in the street outside and sniffing the holes
(with the electronic sniffer) and concluded it was a mains leak.

(Actually I was relatively impressed by that part - he went up and down
the street, making a graph of the gas readings and was fairly confident
where the leak was - and he was bang on too)

So he went to his van to check the maps before calling out a crew - came
back with the bad news that as the mains pipe was right next to some
11KV cables he'd have to call a supervisor. Supervisor came, they hummed
& hawed over the map and readings then called a digging crew. It was now
9pm.

They stopped digging at silly AM - meanwhile the gas man had been in & out
the house every half hour to check the readings.

They found a pipe join that only had 2 of it's 3 bolts fitted. It must
have been like that for 50 years, and maybe some recent HGV had come
down the street and upset things a little (it's a 7.5t limit road)

It was interesting to see the crew smoking as they were digging the
hole. They didn't fix it in the early hours, just left it open and
leaking. It had filled up with water (as it was raining), and you could
see it bubbling quite freely. The morning crew came to fix it, and again
didn't seem concerned having their fag and tea while looking into it,
criticising their colleagues who'd laid it 50 years ago...

So if you're going to call and you think they're going to dig things up,
wait until the morning or you won't get any sleep.

Gordon

Gordon Henderson wrote:
In article ,
DM wrote:

If it is a mains gas smell then I would still report it to Transco. It is
very unlikely to cost you anything IMO and given a couple of tragic
incidents over the years they do like to respond and investigate these issues.

If you are going to report it, a word of advice ... DO NOT report it in
the late afternoon/evening!

There had been a smell of gas round our way for some time - weeks,
not all the time, just the occasional whiff... Got our friendly local
plumber in to check our own house pipe works and it was as sound as a
sound thing, so foolishly called the number ...

After pretending to shut down our own gas, and going through the script
with the phone driod, an engineer was summoned. This was at about 6pm.

I explained the situation, that we get the occasional whiff of gas in
one corner of the room, and very occasionally outside in the street. He
checked our own piping and was happy it wasn't ours..

There then followed many hours of to-ing & fro-in )-: He went round with
the sniffer, inside and outside, to our neighbours and back again, then
started punching holes in the street outside and sniffing the holes
(with the electronic sniffer) and concluded it was a mains leak.

(Actually I was relatively impressed by that part - he went up and down
the street, making a graph of the gas readings and was fairly confident
where the leak was - and he was bang on too)

So he went to his van to check the maps before calling out a crew - came
back with the bad news that as the mains pipe was right next to some
11KV cables he'd have to call a supervisor. Supervisor came, they hummed
& hawed over the map and readings then called a digging crew. It was now
9pm.

They stopped digging at silly AM - meanwhile the gas man had been in & out
the house every half hour to check the readings.

They found a pipe join that only had 2 of it's 3 bolts fitted. It must
have been like that for 50 years, and maybe some recent HGV had come
down the street and upset things a little (it's a 7.5t limit road)

It was interesting to see the crew smoking as they were digging the
hole. They didn't fix it in the early hours, just left it open and
leaking. It had filled up with water (as it was raining), and you could
see it bubbling quite freely. The morning crew came to fix it, and again
didn't seem concerned having their fag and tea while looking into it,
criticising their colleagues who'd laid it 50 years ago...

So if you're going to call and you think they're going to dig things up,
wait until the morning or you won't get any sleep.

Gordon

All in all not too bad a service. Letting it vent is far safer than letting
it potentially migrate under yours or someone else's house.

Given that there have been a couple of incidents of house explosions due to
gas migration under similar circumstances leaving it is probably not the
best option. One lost nights sleep versus that risk shouldn't really be a
concern.

Contrary to popular myth shown in the movies fag ends are pretty poor at
lighting gas or petrol. While combustible materials such as paper and soft
furnishing will light with a cigarette many gases and liquids take either
much higher temperatures or a spark for anything to actually happen.

I'm pretty sure someone did look at this in the last few years where they
threw lit fag ends at puddles of petrol to no effect.

cheers

David

On Tue, 22 Jan 2008 15:07:58 +0000 (UTC) someone who may be Gordon
Henderson wrote this:-

There then followed many hours of to-ing & fro-in )-: He went round with
the sniffer, inside and outside, to our neighbours and back again, then
started punching holes in the street outside and sniffing the holes
(with the electronic sniffer) and concluded it was a mains leak.

I'm glad to hear it. Others haven't been so lucky.

http://www.journalonline.co.uk/news/1002177.aspx outlines the most
well known case, but there have been others. The only remotely good
thing in the whole episode was that Transco, as they then were, did
not appeal against the fine.


--
David Hansen, Edinburgh
I will *always* explain revoked encryption keys, unless RIP prevents me
http://www.opsi.gov.uk/acts/acts2000/00023--e.htm#54

"DM" wrote in message
...
Gordon Henderson wrote:
In article ,
DM wrote:

snip
Gordon

All in all not too bad a service. Letting it vent is far safer than
letting it potentially migrate under yours or someone else's house.

Given that there have been a couple of incidents of house explosions due
to gas migration under similar circumstances leaving it is probably not
the best option. One lost nights sleep versus that risk shouldn't really
be a concern.

Contrary to popular myth shown in the movies fag ends are pretty poor at
lighting gas or petrol. While combustible materials such as paper and soft
furnishing will light with a cigarette many gases and liquids take either
much higher temperatures or a spark for anything to actually happen.

I'm pretty sure someone did look at this in the last few years where they
threw lit fag ends at puddles of petrol to no effect.


Gas is only dangerous in confined spaces where (a) it can reach a point
where the mixture of gas and air becomes explosive and (b) the resultant
damage (falling masonry etc) is itself dangerous - in these circumstances it
represents a very significant hazard (with very high associated risk) to
anyone in the building. There is very little risk working round a leaking
gas main outdoors as it disperses - the worst that might happen is that you
have a sort of blowtorch on your hands - unpleasant and inconvenient,
certainly, but not life threatening. Even then you would need a naked flame
close to the pipe and almost deliberately set fire to it. The worst outdoor
incident I witnessed was during the change to natural gas when they were
venting a 8-12" gas main through 10' standpipes up from the main in the road
(outside my parent's house). Someone drove over the top, shearing the
standpipe off leaving a large hole and a spark ignited the gas. Nothing much
happened except there was an impressive 6-8' bunsen burner flame in the road
(which they duly put a fence round until it could be isolated)!


--
Bob Mannix
(anti-spam is as easy as 1-2-3 - not)


--
Bob Mannix
(anti-spam is as easy as 1-2-3 - not)

The message
from "Bob Mannix" contains these words:

The worst outdoor
incident I witnessed was during the change to natural gas when they were
venting a 8-12" gas main through 10' standpipes up from the main in
the road
(outside my parent's house). Someone drove over the top, shearing the
standpipe off leaving a large hole and a spark ignited the gas.
Nothing much
happened except there was an impressive 6-8' bunsen burner flame in
the road
(which they duly put a fence round until it could be isolated)!

Ha, I can cap that. I was working in Walsall in the mid 70s when someone
digging in the road punctured a gas main which then caught fire. The
flame was 3 or 4 storeys high and the fire brigade was called to damp
down the closest buildings. ISTR the noise was quite impressive as well.

--
Roger Chapman