http://www.screwfix.com/prods/32417

Although I expect some shouting down for asking a gas question in
public, I'll do it anyway:

What is the correct female part to mate with a standard cooker bayonet
above - 1/2" BSP parallel or taper?

I notice that Rocol Threadseal XS (which I use here and there on water
and love it) is rated for gas (natural and LPG - mine is natural). Any
reason not to go for it in preference to gas PTFE?

Those are the only questions - I've been through the checklist:

Line hole through cavity wall with gas proof tube;
Slight downwards angle towards outside where 95% of the run will be;
Seal said tube to wall both sides (I have flame grade mastic)
Seal copper gas pipe to tube on inside only.
Pressure test - have manometer and done this before when I capped the
old supply line off.
Pipe size calcs - done and not a problem,

I don't think I missed anything.

Cheers

Tim

--
Tim Watts

On Nov 29, 12:02*am, Tim Watts wrote:
http://www.screwfix.com/prods/32417

Although I expect some shouting down for asking a gas question in
public, I'll do it anyway:

What is the correct female part to mate with a standard cooker bayonet
above - 1/2" BSP parallel or taper?

I notice that Rocol Threadseal XS (which I use here and there on water
and love it) is rated for gas (natural and LPG - mine is natural). Any
reason not to go for it in preference to gas PTFE?

Those are the only questions - I've been through the checklist:

Line hole through cavity wall with gas proof tube;
Slight downwards angle towards outside where 95% of the run will be;
Seal said tube to wall both sides (I have flame grade mastic)
Seal copper gas pipe to tube on inside only.
Pressure test - have manometer and done this before when I capped the
old supply line off.
Pipe size calcs - done and not a problem,

I don't think I missed anything.

Cheers

Tim

--
Tim Watts

You find parallel threads on things like tank connectors and
connections where there is a shoulder and washer that it buts up to.
You can't seal a parallel thread properly. So if you are wanting to
seal on the thread it has to be taper.
Be sure to wind the thread seal onto the male part in the correct
direction so that it's not "unwound" as you screw the fitting in.
Test all your joints with soapy water/leak detector spray.

On 29/11/10 10:41, harry wrote:
On Nov 29, 12:02 am, Tim wrote:
http://www.screwfix.com/prods/32417

Although I expect some shouting down for asking a gas question in
public, I'll do it anyway:

What is the correct female part to mate with a standard cooker bayonet
above - 1/2" BSP parallel or taper?

I notice that Rocol Threadseal XS (which I use here and there on water
and love it) is rated for gas (natural and LPG - mine is natural). Any
reason not to go for it in preference to gas PTFE?

Those are the only questions - I've been through the checklist:

Line hole through cavity wall with gas proof tube;
Slight downwards angle towards outside where 95% of the run will be;
Seal said tube to wall both sides (I have flame grade mastic)
Seal copper gas pipe to tube on inside only.
Pressure test - have manometer and done this before when I capped the
old supply line off.
Pipe size calcs - done and not a problem,

I don't think I missed anything.

Cheers

Tim

--
Tim Watts

You find parallel threads on things like tank connectors and
connections where there is a shoulder and washer that it buts up to.
You can't seal a parallel thread properly. So if you are wanting to
seal on the thread it has to be taper.

Righty ho - so the female should be taper and presumably the male (on
the bayonet) is parallel?

Be sure to wind the thread seal onto the male part in the correct
direction so that it's not "unwound" as you screw the fitting in.

Thanks for that. I've done "iron" joints before (with PTFE,
hemp+bosswhite and Threadseal XS) - but mostly bibtaps and CH parts
where there wasn't any doubt as to the nature of the threads. I just
wasn't sure how the taper was arranged with the gas bayonets.

Test all your joints with soapy water/leak detector spray.

Always do I'm very fussy in that regard - I do a full pressure drop
test at the meter too whenever I touch anything. I do have a good tome
on gas which has the pipe sizing calcs explained and a copy of the gas regs.

Cheers and thanks,

Tim

--
Tim Watts

On Nov 29, 11:08*am, Tim Watts wrote:
On 29/11/10 10:41, harry wrote:





On Nov 29, 12:02 am, Tim *wrote:
http://www.screwfix.com/prods/32417

Although I expect some shouting down for asking a gas question in
public, I'll do it anyway:

What is the correct female part to mate with a standard cooker bayonet
above - 1/2" BSP parallel or taper?

I notice that Rocol Threadseal XS (which I use here and there on water
and love it) is rated for gas (natural and LPG - mine is natural). Any
reason not to go for it in preference to gas PTFE?

Those are the only questions - I've been through the checklist:

Line hole through cavity wall with gas proof tube;
Slight downwards angle towards outside where 95% of the run will be;
Seal said tube to wall both sides (I have flame grade mastic)
Seal copper gas pipe to tube on inside only.
Pressure test - have manometer and done this before when I capped the
old supply line off.
Pipe size calcs - done and not a problem,

I don't think I missed anything.

Cheers

Tim

--
Tim Watts

You find parallel threads on things like tank connectors and
connections where there is a shoulder and washer that it buts up to.
You can't seal a parallel thread properly. So if you are wanting to
seal on the thread it has to be taper.

Righty ho - so the female should be taper and presumably the male (on
the bayonet) is parallel?

Be sure to wind the thread seal onto the male part in the correct
direction so that it's not "unwound" as you screw the fitting in.

Thanks for that. I've done "iron" joints before (with PTFE,
hemp+bosswhite and Threadseal XS) - but mostly bibtaps and CH parts
where there wasn't any doubt as to the nature of the threads. I just
wasn't sure how the taper was arranged with the gas bayonets.

Test all your *joints with soapy water/leak detector spray.

Always do I'm very fussy in that regard - I do a full pressure drop
test at the meter too whenever I touch anything. I do have a good tome
on gas which has the pipe sizing calcs explained and a copy of the gas regs.

Cheers and thanks,

Tim

--
Tim Watts- Hide quoted text -

- Show quoted text -
Both parts should be taper. As the parts are screwed together, the
"slack" in the thread gets smaller and squeezes up the joint
material. It is the convention that in a correct joint, one complete
thread shows when the thing is screwed home. On expensive fittings
this works out. On the cheap ones sometimes not. All down to quality
control.
However you find some of the cheaper makes of fittings eg sockets they
have run the tap straight through so it ends up parallel. I always
thought this a bit dodgy though it never seemed to cause a problem in
practice.

On Nov 29, 10:41*am, harry wrote:

You can't seal a parallel thread properly. So if you are wanting to
seal on the thread it has to be taper.

Whilst that's true for a compression fitting (metal-metal or taped)
it's no longer so true wiith liquid pipe thread sealers.

How acceptable is it to use them in this way, in terms of gas and
quality of workmanship? They certainly seem to have replaced the old
"packing with washers" tricks for water plumbing where you need a
thread to stop with a particular orientation.