I had to cap off the hot and cold pipes to my kitchen sink last week
while I'm re-plumbing the kitchen. All Wickes had in stock was copper
push-fit end-caps, which did the job a treat, but I noticed that the
packet says "not for use with gas" (or similar words to that effect).

Just out of idle curiosity, why is that? I would have thought that, if
they're good enough to form an air-tight seal to withhold mains water
at, say, 5 bar then they would comfortably cope with gas at 20-odd
millibars or whatever it is. Obviously, there must be a reason, but what
is it?

I happened to notice that the bloke who installed our new combi last
year used a plastic push-fit end-cap to cap off the gas supply (probably
for all of about 2 or 3 hours while he plumbed in the new boiler). Was
that, strictly speaking, a bit "iffy" (even though the supply would have
been off at the meter, and presumably disced-off or disconnected from
the meter too) or is there something about the plastic end-caps that
make them suitable for gas?

Also, on a similar tack, why is there a separate (thicker?) type of PTFE
tape for gas? Again, if the standard PTFE tape for use with water is
good enough at typical mains water pressures, why is it no good for gas
at a fraction of the pressure?

Enquiring minds, etc. etc.
--
Chris Cowley

Chris Cowley wrote:
I had to cap off the hot and cold pipes to my kitchen sink last week
while I'm re-plumbing the kitchen. All Wickes had in stock was copper
push-fit end-caps, which did the job a treat, but I noticed that the
packet says "not for use with gas" (or similar words to that effect).

Just out of idle curiosity, why is that? I would have thought that, if
they're good enough to form an air-tight seal to withhold mains water
at, say, 5 bar then they would comfortably cope with gas at 20-odd
millibars or whatever it is. Obviously, there must be a reason, but what
is it?

It'll seal OK, but is not regs compliant. This is for the same reason
plastic pipe isn't allowed for use with gas - in the even of a local
fire, it will give way very quickly.


I happened to notice that the bloke who installed our new combi last
year used a plastic push-fit end-cap to cap off the gas supply (probably
for all of about 2 or 3 hours while he plumbed in the new boiler). Was
that, strictly speaking, a bit "iffy" (even though the supply would have
been off at the meter, and presumably disced-off or disconnected from
the meter too) or is there something about the plastic end-caps that
make them suitable for gas?

This is common practice, but I don't know if it is strictly speaking
incorrect. It poses no danger if it's just a temporary measure for a
couple of hours while working on the system.


Also, on a similar tack, why is there a separate (thicker?) type of PTFE
tape for gas? Again, if the standard PTFE tape for use with water is
good enough at typical mains water pressures, why is it no good for gas
at a fraction of the pressure?

This one I never figured out.


--
Grunff

In an earlier contribution to this discussion,
Grunff wrote:


It'll seal OK, but is not regs compliant. This is for the same reason
plastic pipe isn't allowed for use with gas

Unless it happens to be a gas *main*!
--
Cheers,
Roger
______
Please reply to newsgroup.
Reply address IS valid, but is disposable in the event of excessive
spam.

"Roger Mills (aka Set Square)" wrote in message
...
In an earlier contribution to this discussion,
Grunff wrote:


It'll seal OK, but is not regs compliant. This is for the same reason
plastic pipe isn't allowed for use with gas

Unless it happens to be a gas *main*!

In which we used rubber bungs as temporary solution.

On Mon, 20 Feb 2006 15:56:58 +0000, Roger Mills (aka Set Square) wrote:

In an earlier contribution to this discussion,
Grunff wrote:


It'll seal OK, but is not regs compliant. This is for the same reason
plastic pipe isn't allowed for use with gas

Unless it happens to be a gas *main*!
.... underground.

--
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

On Mon, 20 Feb 2006 15:42:41 +0000, Grunff wrote:

It'll seal OK, but is not regs compliant. This is for the same reason
plastic pipe isn't allowed for use with gas - in the even of a local
fire, it will give way very quickly.

Ah, that makes perfect sense. I had a poke about with one of the copper
fittings before I used it and they seem to have a rubber O-ring that
compresses around the circumference of the pipe to make the seal. I
don't suppose that would last too long in a fire.

Actually, thinking about it, I'm not sure I'd like to use push-fit
connectors at all for anything long-term - the compressed O-ring will
perish at some point, maybe a few years down the line, but even so
someone would get wet feet at some point. There's something slightly
bodgy about them IMHO.
--
Chris Cowley

On Mon, 20 Feb 2006 16:30:24 +0000, Chris Cowley
wrote:

On Mon, 20 Feb 2006 15:42:41 +0000, Grunff wrote:

It'll seal OK, but is not regs compliant. This is for the same reason
plastic pipe isn't allowed for use with gas - in the even of a local
fire, it will give way very quickly.

Ah, that makes perfect sense. I had a poke about with one of the copper
fittings before I used it and they seem to have a rubber O-ring that
compresses around the circumference of the pipe to make the seal. I
don't suppose that would last too long in a fire.

Actually, thinking about it, I'm not sure I'd like to use push-fit
connectors at all for anything long-term - the compressed O-ring will
perish at some point, maybe a few years down the line, but even so
someone would get wet feet at some point. There's something slightly
bodgy about them IMHO.


The manufacturers are giving 50 year guarantees, so they feel pretty
confident and the O-rings are not conventional rubber.

The main point is to cut the tube squarely and cleanly with the proper
cutter when assembling


--

..andy

"Andy Hall" wrote in message
...
On Mon, 20 Feb 2006 16:30:24 +0000, Chris Cowley
wrote:

On Mon, 20 Feb 2006 15:42:41 +0000, Grunff wrote:

Actually, thinking about it, I'm not sure I'd like to use push-fit
connectors at all for anything long-term - the compressed O-ring will
perish at some point, maybe a few years down the line, but even so
someone would get wet feet at some point. There's something slightly
bodgy about them IMHO.


The manufacturers are giving 50 year guarantees, so they feel pretty
confident and the O-rings are not conventional rubber.

The main point is to cut the tube squarely and cleanly with the proper
cutter when assembling

So far two materials which were "guaranteed for 50 years" that I have used
have failed before 10 years. Specifically, plasic push-fit plumbing (now
replaced with soldered copper) and a putty substitute (now replaced with
proper putty). There seems to be a pattern! Anyway, how do they know these
_new_ materials will last 50 years? I increasingly find myself going towards
traditional methods/materials.

On Mon, 20 Feb 2006 16:56:03 -0000 Russel Sprout wrote :
Anyway, how do they know these _new_ materials
will last 50 years? I increasingly find myself going towards
traditional methods/materials.

They 'know' by accelerated testing. But when you look back there are
more than a few cases where adopting new materials proved to be a bad
idea - high alumina cement for example - but plenty more where the
new has proved to be much more durable that what it replaced -
concrete roof tiles, PVC cable, copper tube for starters.

--
Tony Bryer SDA UK 'Software to build on' http://www.sda.co.uk
Free SEDBUK boiler database browser http://www.sda.co.uk/qsedbuk.htm
[Latest version QSEDBUK 1.12 released 8 Dec 2005]

"Russel Sprout" wrote in message
...

"Andy Hall" wrote in message
...
On Mon, 20 Feb 2006 16:30:24 +0000, Chris Cowley
wrote:

On Mon, 20 Feb 2006 15:42:41 +0000, Grunff wrote:

Actually, thinking about it, I'm not sure I'd like to use push-fit
connectors at all for anything long-term - the compressed O-ring will
perish at some point, maybe a few years down the line, but even so
someone would get wet feet at some point. There's something slightly
bodgy about them IMHO.


The manufacturers are giving 50 year guarantees, so they feel pretty
confident and the O-rings are not conventional rubber.

The main point is to cut the tube squarely and cleanly with the proper
cutter when assembling

So far two materials which were "guaranteed for 50 years" that I have used
have failed before 10 years. Specifically, plasic push-fit plumbing (now
replaced with soldered copper) and a putty substitute (now replaced with
proper putty). There seems to be a pattern! Anyway, how do they know these
_new_ materials will last 50 years? I increasingly find myself going
towards
traditional methods/materials.

Soldered copper is by far ten best pipe system.

Russel Sprout wrote:

So far two materials which were "guaranteed for 50 years" that I have used
have failed before 10 years. Specifically, plasic push-fit plumbing (now
replaced with soldered copper)

What was the actual mode of failure, and how long had it lasted?

David

On Mon, 20 Feb 2006 16:45:01 +0000, Andy Hall wrote:

The manufacturers are giving 50 year guarantees, so they feel pretty
confident and the O-rings are not conventional rubber.

The main point is to cut the tube squarely and cleanly with the proper
cutter when assembling

Well, a 50 year guarantee does sound mighty impressive I must say, but
even so, I'm going to remain with the flat-earthers on this one and
stick to my olde fashionde solder and compression fittings, I think!

I wonder what those O-rings are made of that will not crack or perish
under compression for 50 years?
--
Chris Cowley

"Chris Cowley" wrote in message
...
On Mon, 20 Feb 2006 16:45:01 +0000, Andy Hall wrote:

The manufacturers are giving 50 year guarantees, so they feel pretty
confident and the O-rings are not conventional rubber.

The main point is to cut the tube squarely and cleanly with the proper
cutter when assembling

Well, a 50 year guarantee does sound mighty impressive I must say, but
even so, I'm going to remain with the flat-earthers on this one and
stick to my olde fashionde solder and compression fittings, I think!

I wonder what those O-rings are made of that will not crack or perish
under compression for 50 years?

...and movement with expansion and contraction.

"Andy Hall" wrote in message
...
On Mon, 20 Feb 2006 16:30:24 +0000, Chris Cowley
wrote:

On Mon, 20 Feb 2006 15:42:41 +0000, Grunff wrote:

It'll seal OK, but is not regs compliant. This is for the same reason
plastic pipe isn't allowed for use with gas - in the even of a local
fire, it will give way very quickly.

Ah, that makes perfect sense. I had a poke about with one of the copper
fittings before I used it and they seem to have a rubber O-ring that
compresses around the circumference of the pipe to make the seal. I
don't suppose that would last too long in a fire.

Actually, thinking about it, I'm not sure I'd like to use push-fit
connectors at all for anything long-term - the compressed O-ring will
perish at some point, maybe a few years down the line, but even so
someone would get wet feet at some point. There's something slightly
bodgy about them IMHO.

The manufacturers are giving 50 year guarantees, so they feel pretty
confident and the O-rings are not conventional rubber.

Pushfit fittings should be avoided. Many pro avoid them like then plague.
They can hold for weeks then fail either in the O ring or the grab ring.
You can use brass compression fitting on plastic with the olive wrapped in
PTFE. Cheap and better and easily demountable. Hep2O and Polyplumb fitting
have been known to have the nuts work loose.

On Mon, 20 Feb 2006 17:43:04 -0000, "Doctor Drivel"
wrote:

Pushfit fittings should be avoided. Many pro avoid them like then plague.
They can hold for weeks then fail either in the O ring or the grab ring.
You can use brass compression fitting on plastic with the olive wrapped in
PTFE. Cheap and better and easily demountable. Hep2O and Polyplumb fitting
have been known to have the nuts work loose.

Oh gawd! Perhaps I should've kept my big gob shut...
--
Chris Cowley

On Mon, 20 Feb 2006 17:43:04 -0000, "Doctor Drivel"
wrote:


Pushfit fittings should be avoided.

Only if you don't use them properly and don't follow the instructions.
Ears gone red yet?

Many pro avoid them like then plague.

Many pros don't fit condensing boilers and you criticise them.


They can hold for weeks then fail either in the O ring or the grab ring.
You can use brass compression fitting on plastic with the olive wrapped in
PTFE. Cheap and better and easily demountable.

That really is a bodge.


Hep2O and Polyplumb fitting
have been known to have the nuts work loose.

--

..andy

Chris Cowley wrote:

Actually, thinking about it, I'm not sure I'd like to use push-fit
connectors at all for anything long-term - the compressed O-ring will
perish at some point, maybe a few years down the line, but even so
someone would get wet feet at some point. There's something slightly
bodgy about them IMHO.

O rings have been used in industry for a very long time, and the aging
characteristics of the rubbers used (mostly EPDM) are very well
understood. As long as the installation is carried out correctly in the
first place, the service life will be 30+ years, more likely 50+ years.
This is plenty for domestic use.


--
Grunff

"Grunff" wrote in message
...
Chris Cowley wrote:
I had to cap off the hot and cold pipes to my kitchen sink last week
while I'm re-plumbing the kitchen. All Wickes had in stock was copper
push-fit end-caps, which did the job a treat, but I noticed that the
packet says "not for use with gas" (or similar words to that effect).

Just out of idle curiosity, why is that? I would have thought that, if
they're good enough to form an air-tight seal to withhold mains water
at, say, 5 bar then they would comfortably cope with gas at 20-odd
millibars or whatever it is. Obviously, there must be a reason, but what
is it?

It'll seal OK, but is not regs compliant. This is for the same reason
plastic pipe isn't allowed for use with gas - in the even of a local fire,
it will give way very quickly.

Some fittings will hold water but not gas. A copper pushfit on copper pipe
is not a fire hazard it itself. Plastic pushfits would be. Restrictor
elbows on gas fires have neoprene washers in them.

I happened to notice that the bloke who installed our new combi last
year used a plastic push-fit end-cap to cap off the gas supply (probably
for all of about 2 or 3 hours while he plumbed in the new boiler). Was
that, strictly speaking, a bit "iffy" (even though the supply would have
been off at the meter, and presumably disced-off or disconnected from
the meter too) or is there something about the plastic end-caps that
make them suitable for gas?

This is common practice, but I don't know if it is strictly speaking
incorrect. It poses no danger if it's just a temporary measure for a
couple of hours while working on the system.

It is in effect illegal, but he is there and temporary, so not dangerous.

Also, on a similar tack, why is there a separate (thicker?) type of PTFE
tape for gas? Again, if the standard PTFE tape for use with water is
good enough at typical mains water pressures, why is it no good for gas
at a fraction of the pressure?

This one I never figured out.

Some threads are course and the thicker tape fills in the gaps. Also it
supposed to have a mix that is more suitable for gas. No many pros do not
it preferring the tried and tested jointing compound which is also quicker
to apply.

On Mon, 20 Feb 2006 15:33:58 +0000, Chris Cowley
wrote:

I had to cap off the hot and cold pipes to my kitchen sink last week
while I'm re-plumbing the kitchen. All Wickes had in stock was copper
push-fit end-caps, which did the job a treat, but I noticed that the
packet says "not for use with gas" (or similar words to that effect).

Just out of idle curiosity, why is that? I would have thought that, if
they're good enough to form an air-tight seal to withhold mains water
at, say, 5 bar then they would comfortably cope with gas at 20-odd
millibars or whatever it is. Obviously, there must be a reason, but what
is it?


I think that that is probably part of the clue.

The metal teeth in the fitting dig into the pipe as one attempts to
pull it or with pressure from the water - the greater, the more.

Since gas is at a tiny fraction of that pressure, this effect doesn't
happen. Whether that would lead to a leak is another thing, but the
manufacturers certify their products for an application.

For example, I have some John Guest nylon airline and the push fit
fittings to go with that. They are good for so many bar of
compressed air. The fittings are slightly different to the water
ones.


I happened to notice that the bloke who installed our new combi last
year used a plastic push-fit end-cap to cap off the gas supply (probably
for all of about 2 or 3 hours while he plumbed in the new boiler). Was
that, strictly speaking, a bit "iffy" (even though the supply would have
been off at the meter, and presumably disced-off or disconnected from
the meter too) or is there something about the plastic end-caps that
make them suitable for gas?

It's a requirement for a fitter to cap the supply if he is going to
leave it unattended. I suppose that by the book, it should be a
fitting rated for gas use.



Also, on a similar tack, why is there a separate (thicker?) type of PTFE
tape for gas? Again, if the standard PTFE tape for use with water is
good enough at typical mains water pressures, why is it no good for gas
at a fraction of the pressure?

I had always understood it to be because taper threads are typically
used meaning greater gaps to seal and the gas tape is thicker.



--

..andy

Also, on a similar tack, why is there a separate (thicker?) type of PTFE
tape for gas? Again, if the standard PTFE tape for use with water is
good enough at typical mains water pressures, why is it no good for gas
at a fraction of the pressure?

Enquiring minds, etc. etc.
--
Chris Cowley

Maybe it has something to do with the size of the molecules as much as the
pressure.

Grumble

On Mon, 20 Feb 2006 16:04:29 +0000 (UTC), "Grumble"
wrote:

| Also, on a similar tack, why is there a separate (thicker?) type of PTFE
| tape for gas? Again, if the standard PTFE tape for use with water is
| good enough at typical mains water pressures, why is it no good for gas
| at a fraction of the pressure?
|
| Enquiring minds, etc. etc.
| --
| Chris Cowley
|
|Maybe it has something to do with the size of the molecules as much as the
|pressure.

Also the risk.
Water leak, things get wet.
Gas leak, you may get an explosion.
--
Dave Fawthrop dave hyphenologist co uk
Freedom of Speech, Expression, Religion, and Democracy are
the keys to Civilization, together with legal acceptance of
Fundamental Human rights.

On Mon, 20 Feb 2006 16:04:29 +0000 (UTC), "Grumble"
wrote:

Also, on a similar tack, why is there a separate (thicker?) type of PTFE
tape for gas? Again, if the standard PTFE tape for use with water is
good enough at typical mains water pressures, why is it no good for gas
at a fraction of the pressure?

Enquiring minds, etc. etc.
--
Chris Cowley

Maybe it has something to do with the size of the molecules as much as the
pressure.

Well, that's certainly a possibility I suppose. It would be nice to know
for sure though. Maybe the gas PTFE tape is somehow denser than the
standard stuff?
--
Chris Cowley

On Mon, 20 Feb 2006 15:33:58 +0000, Chris Cowley wrote:

I had to cap off the hot and cold pipes to my kitchen sink last week
while I'm re-plumbing the kitchen. All Wickes had in stock was copper
push-fit end-caps, which did the job a treat, but I noticed that the
packet says "not for use with gas" (or similar words to that effect).

Just out of idle curiosity, why is that? I would have thought that, if
they're good enough to form an air-tight seal to withhold mains water
at, say, 5 bar then they would comfortably cope with gas at 20-odd
millibars or whatever it is. Obviously, there must be a reason, but what
is it?

I happened to notice that the bloke who installed our new combi last
year used a plastic push-fit end-cap to cap off the gas supply (probably
for all of about 2 or 3 hours while he plumbed in the new boiler). Was
that, strictly speaking, a bit "iffy" (even though the supply would have
been off at the meter, and presumably disced-off or disconnected from
the meter too) or is there something about the plastic end-caps that
make them suitable for gas?

Also, on a similar tack, why is there a separate (thicker?) type of PTFE
tape for gas? Again, if the standard PTFE tape for use with water is
good enough at typical mains water pressures, why is it no good for gas
at a fraction of the pressure?

1) Not approved, so even if they were the most gas tight fitting in the
world they simply would not be permitted.
2) Have plastic parts whose fire resistance is questionable.
3) The firmness of the connection is enhanced by the internal pressure.
Clearly pressures measured in bar have a bigger effect than those in mbar.


--
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