A couple of questions regarding extending gas pipework:

1) It is illegal to run gas pipe in a cavity wall because of the possibility
of gas build-up, does this mean it is preferable where I have the choice to
run gas pipe along a wall rather than under floorboards?

2) How do I clear the existing pipe of gas before soldering the new pipe on?
The pipe comes down from the meter, under the floor (presumably horizontally
but I've got no way of telling) and then up in a cupboard which is where I
will be making the join. So I would imagine most gas will escape once I open
up the old pipe - but with things like this it is best to make sure! Should
I open up the test nipple at the meter to aid dispersion? I don't have any
gas analysis devices.
N.B. I am fully aware of the need to purge air from the new installation.


Thanks

Pete.

"PM" wrote in message
...
A couple of questions regarding extending gas pipework:

1) It is illegal to run gas pipe in a cavity
wall because of the possibility
of gas build-up, does this mean it
is preferable where I have the choice to
run gas pipe along a wall rather than
under floorboards?

Under boards is fine as it is ventilated on the ground floor and enough
space under on suspended floors too.

2) How do I clear the existing pipe
of gas before soldering the new pipe on?
The pipe comes down from the meter,
under the floor (presumably horizontally
but I've got no way of telling) and then up
in a cupboard which is where I
will be making the join. So I would imagine
most gas will escape once I open
up the old pipe - but with things like this it
is best to make sure! Should
I open up the test nipple at the meter to
aid dispersion? I don't have any
gas analysis devices.
N.B. I am fully aware of the need to purge air from the new installation.

Turn off the gas and undo the meter outlet union. Between the meter horn and
the union insert a lid from say a flux tin. This prevents any flashbacks
down the pipe from blowing the meter. There is no need to get rid of the gas
in a small copper gas pipe. In larger systems the gas has to be pumped from
the pipe via a flame trap hose to outside.

In reality a flame trap hose is needed on an installation when purging too.
Few are ever used on domestic systems.

On Wed, 14 Jun 2006 13:23:40 +0100, PM wrote:

A couple of questions regarding extending gas pipework:

1) It is illegal to run gas pipe in a cavity wall because of the possibility
of gas build-up, does this mean it is preferable where I have the choice to
run gas pipe along a wall rather than under floorboards?

2) How do I clear the existing pipe of gas before soldering the new pipe on?
The pipe comes down from the meter, under the floor (presumably horizontally
but I've got no way of telling) and then up in a cupboard which is where I
will be making the join. So I would imagine most gas will escape once I open
up the old pipe - but with things like this it is best to make sure! Should
I open up the test nipple at the meter to aid dispersion? I don't have any
gas analysis devices.
N.B. I am fully aware of the need to purge air from the new installation.

As always if you need to ask you probably shouldn't be doing it...

1) Through cavity is fine but there are extra rules. See BS 6891

2) No need to purge gas from the pipes. You will need to seal the meter
outlet if working within 2m of the meter. The gas can only burn if comes
into contact with air. Even when unsoldering fittings the most you even
get is a small flame which goes out in a few seconds.



--
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
Gas Fitting Standards Docs he http://www.makewrite.demon.co.uk/GasFittingStandards

"Ed Sirett" wrote in message
news
On Wed, 14 Jun 2006 13:23:40 +0100, PM wrote:

A couple of questions regarding extending gas pipework:

1) It is illegal to run gas pipe in a cavity wall because of the
possibility
of gas build-up, does this mean it is preferable where I have the choice
to
run gas pipe along a wall rather than under floorboards?

2) How do I clear the existing pipe of gas before soldering the new pipe
on?
The pipe comes down from the meter, under the floor (presumably
horizontally
but I've got no way of telling) and then up in a cupboard which is where
I
will be making the join. So I would imagine most gas will escape once I
open
up the old pipe - but with things like this it is best to make sure!
Should
I open up the test nipple at the meter to aid dispersion? I don't have
any
gas analysis devices.
N.B. I am fully aware of the need to purge air from the new installation.

As always if you need to ask you probably shouldn't be doing it...

1) Through cavity is fine but there are extra rules. See BS 6891

2) No need to purge gas from the pipes. You will need to seal the meter
outlet if working within 2m of the meter. The gas can only burn if comes
into contact with air. Even when unsoldering fittings the most you even
get is a small flame which goes out in a few seconds.

I have seen a flash dow 6 metres of pipe and a boom as the guts of the meter
blew.

In message ews.net,
Doctor Drivel writes

N.B. I am fully aware of the need to purge air from the new installation.

As always if you need to ask you probably shouldn't be doing it...

1) Through cavity is fine but there are extra rules. See BS 6891

2) No need to purge gas from the pipes. You will need to seal the meter
outlet if working within 2m of the meter. The gas can only burn if comes
into contact with air. Even when unsoldering fittings the most you even
get is a small flame which goes out in a few seconds.

I have seen a flash dow 6 metres of pipe and a boom as the guts of the
meter blew.

I bet you have

--
geoff

"raden" wrote in message
...
In message ews.net,
Doctor Drivel writes

N.B. I am fully aware of the need to purge air from the new
installation.

As always if you need to ask you probably shouldn't be doing it...

1) Through cavity is fine but there are extra rules. See BS 6891

2) No need to purge gas from the pipes. You will need to seal the meter
outlet if working within 2m of the meter. The gas can only burn if comes
into contact with air. Even when unsoldering fittings the most you even
get is a small flame which goes out in a few seconds.

I have seen a flash dow 6 metres of pipe and a boom as the guts of the
meter blew.

I bet you have

Maxie, I did. Boom, then meter not working. I have also seen one blow as a
blowtorch was passed over a meter horn and the meter was disconnected.
Maxie, I have seen many things.

The message ews.net
from "Doctor Drivel" contains these words:

Maxie, I have seen many things.

Attack ships on fire off the shoulder of Orion?

--
Skipweasel
Pay no attention to that man behind the curtain.

AIUI it is sometimes safer to ignite the gas in the pipe deliberately after
disconnecion from the meter.
An aquaintance of mine was blanking off a connection when the gas in the
pipe ignited and blew the cap across the room.

Phil

"Ed Sirett" wrote in message
news

As always if you need to ask you probably shouldn't be doing it...


First time for everything! I've read up a lot (including your FAQs) but
there are some areas such as this where I'm not sure. My mind has been made
up to DIY mainly because of the incompetence and obvious dishonesty of the
"tradesmen" I have had round for gas work in the past, and for quoting for a
new boiler.

1) Through cavity is fine but there are extra rules. See BS 6891

Through cavity yes, along length of cavity no because of gas build-up. So is
it better to avoid under floorboards if possible or is it fine as Drivel
says? I have the choice of running the pipe in the corner of the ceiling
(unsightly) or under floorboards.



2) No need to purge gas from the pipes. You will need to seal the meter
outlet if working within 2m of the meter. The gas can only burn if comes
into contact with air. Even when unsoldering fittings the most you even
get is a small flame which goes out in a few seconds.


Thanks!

On Wed, 14 Jun 2006 22:16:24 +0100, Doctor Drivel wrote:


"Ed Sirett" wrote in message
news
On Wed, 14 Jun 2006 13:23:40 +0100, PM wrote:

A couple of questions regarding extending gas pipework:

1) It is illegal to run gas pipe in a cavity wall because of the
possibility
of gas build-up, does this mean it is preferable where I have the choice
to
run gas pipe along a wall rather than under floorboards?

2) How do I clear the existing pipe of gas before soldering the new pipe
on?
The pipe comes down from the meter, under the floor (presumably
horizontally
but I've got no way of telling) and then up in a cupboard which is where
I
will be making the join. So I would imagine most gas will escape once I
open
up the old pipe - but with things like this it is best to make sure!
Should
I open up the test nipple at the meter to aid dispersion? I don't have
any
gas analysis devices.
N.B. I am fully aware of the need to purge air from the new installation.

As always if you need to ask you probably shouldn't be doing it...

1) Through cavity is fine but there are extra rules. See BS 6891

2) No need to purge gas from the pipes. You will need to seal the meter
outlet if working within 2m of the meter. The gas can only burn if comes
into contact with air. Even when unsoldering fittings the most you even
get is a small flame which goes out in a few seconds.

I have seen a flash dow 6 metres of pipe and a boom as the guts of the meter
blew.

What was the pipe diameter?
Pure gas can't go 'boom' as it's concentration is way above the UEL.


--
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
Gas Fitting Standards Docs he http://www.makewrite.demon.co.uk/GasFittingStandards

On Thu, 15 Jun 2006 08:49:44 +0100, PM wrote:


"Ed Sirett" wrote in message
news

1) Through cavity is fine but there are extra rules. See BS 6891

Through cavity yes, along length of cavity no because of gas build-up. So is
it better to avoid under floorboards if possible or is it fine as Drivel
says? I have the choice of running the pipe in the corner of the ceiling
(unsightly) or under floorboards.


A link to BS 6891 can be found under 'gas fitting standards' below.
If the under floor space is ventilated then there is no problem, this is
common practice. It is quite awkward to get the pipes under the floor in
these circumstances. Compression joints should not be used.


--
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
Gas Fitting Standards Docs he http://www.makewrite.demon.co.uk/GasFittingStandards

Guy King wrote:

Attack ships on fire off the shoulder of Orion?
No.

Orions on fire on the hard shoulder.
Yes.

The message .com
from "Aidan" contains these words:

Attack ships on fire off the shoulder of Orion?
No.

Orions on fire on the hard shoulder.
Yes.

You've been watching "Nonrunner", innit.

--
Skipweasel
Pay no attention to that man behind the curtain.

"Ed Sirett" wrote in message
news
On Wed, 14 Jun 2006 13:23:40 +0100, PM wrote:

A couple of questions regarding extending gas pipework:

1) It is illegal to run gas pipe in a cavity wall because of the
possibility
of gas build-up, does this mean it is preferable where I have the choice
to
run gas pipe along a wall rather than under floorboards?

2) How do I clear the existing pipe of gas before soldering the new pipe
on?
The pipe comes down from the meter, under the floor (presumably
horizontally
but I've got no way of telling) and then up in a cupboard which is where
I
will be making the join. So I would imagine most gas will escape once I
open
up the old pipe - but with things like this it is best to make sure!
Should
I open up the test nipple at the meter to aid dispersion? I don't have
any
gas analysis devices.
N.B. I am fully aware of the need to purge air from the new
installation.

As always if you need to ask you probably shouldn't be doing it...

1) Through cavity is fine but there are extra rules. See BS 6891

2) No need to purge gas from the pipes. You will need to seal the meter
outlet if working within 2m of the meter. The gas can only burn if comes
into contact with air. Even when unsoldering fittings the most you even
get is a small flame which goes out in a few seconds.


When I cut the old pipe ready to solder the new pipe on, won't the gas mix
with air at that point? The old pipe is vertical up a wall and I will be
cutting it about a foot from the floor. Won't the gas will rise out of the
existing pipe so could be in the 5-15% concentration either above the pipe,
or within the pipe?