Cutting into wall-mounted CH copper pipe ?

SO following the sage advice here, fitting an external expansion vessel seems to be the way to go.
Seems they need to be plumbed into the CH return pipe ?
On my boiler, this is a larger (1" ?) copper pipe which runs through the ceiling into the boiler, and is fixed by wall mounted clips, so it's about 8mm from the wall.
I can't see anyway to lift it off the clips without some straining which I would rather avoid.
Presumably I need to insert a "T" piece into the pipe ... I'm happy to use pre-soldered bits (have done this before elsewhere, with an asbestos mat behind). But is there a way to cut out the necessary section without disturbing the pipe (too much) ?
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On 17/05/2017 11:43, Jethro_uk wrote:

ANGLE GRINDER!!!!
More mundanely: Reciprocating saw or hacksaw. Very hard to get a nice square cut though.
None of the pipe cutters will fit in 8mm.
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On 17/05/2017 11:56, GB wrote:

http://www.screwfix.com/p/rothenberger-automatic-tube-cutter-28mm/84356
If you can spring the pipe away from the wall a bit.

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On Wed, 17 May 2017 11:59:14 +0100, GB wrote:

I'll do some exploring ... I might be able to tease the pipe a few more mm away.
I could always tap into the pipe the other side of the ceiling (in the loft). But that seems to me to be replacing an inaccessible component that has failed with another inaccessible component.
Thinking about it (in for a penny ...) if I disconnect the pipe from the bottom (where it goes into the boiler) then I will probably have enough play to run a pipe cutter around it.
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On 17/05/17 12:05, Jethro_uk wrote:

That's what I said.
The number of times I have had to relearn the lesson 'trying to dismantle it less always leads to more work eventually'
Taking off the entire back axle to get seized brake drums and hydraulics apart.
Much easier.
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On Wed, 17 May 2017 12:30:26 +0100, The Natural Philosopher wrote:

+1
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On 5/17/2017 12:05 PM, Jethro_uk wrote:

But if you can get into the loft to fit it, it's not inaccessible is it. The other thing I would suggest is fitting a ball-valve and a drain point on the branch so that you can isolate and drain it easily if you want to check the pressure and/or recharge it some time in the future. This is what I have done, anyway. Just given it its first check / recharge in about 15 years.
Important not to accidentally leave it valved off of course.
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On Wed, 17 May 2017 14:26:14 +0100, newshound wrote:

cutter-28mm/84356

True - but by that token then technically the original expansion vessel isn't inaccessible. The section of loft involved is a ****ing pig to get to - need to squeeze through a tiny gap followed by a 15 metre crawl over joists.

Ah, good tip ! Thanks.

:)
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On 5/17/2017 2:36 PM, Jethro_uk wrote:

OK! That's inaccessible! As I think others have said, the exact location that you fit it in the circuit is not particularly critical. Mine is about the size of a football (the next size up from the smallest), you need to find a convenient bit of dead space for it. There's no flow, of course (other than when filling) so it can always be fitted with microbore if it needs to be a little distance away from main flow or return pipes (which are probably 22 mm, unless it is a very old installation). Also, mine is actually fitted on a (flexible) filling loop because that was the most convenient way to do it. That way it can be unhooked from the bracket and lowered, making the schraeder valve more accessible for checking/repressurising.

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On Wed, 17 May 2017 16:09:40 +0100, newshound wrote:

As luck would have it, there's acres of space next to the boiler in our utility room - mounted up high it would never be seen.
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On 17/05/2017 12:05, Jethro_uk wrote:

You have tried to recharge the original one? Remember than when recharging that water is incompressible so you have to have somewhere open to let the water out as you pump the air into the expansion bottle. If you don't then you will only get a small amount of air into the expansion bottle and it will appear to not work. When first fitted they are full of air and have no water in them. After a recharge they should also be ful of air with no water in them. They only get water in once you pressurise the system.
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On Wed, 17 May 2017 15:10:57 +0100, dennis@home wrote:

I did a few years ago. Cover off, scrabbling around behind the boiler to find the valve while perched on top of the washing machine !

I remember that - in fact it was probably advice from here :)

The fact I did it, and it has _slowly_ gone back suggests a small leak. For various reasons I have decided this is the time to nail it "properly".
Given that external expansion vessels are hardly hard to come by, it's a source of curiosity as to why boilers have them built in at all.
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On 17/05/2017 15:13, Jethro_uk wrote:

Ease of fitting.
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On Wed, 17 May 2017 15:10:57 +0100, dennis@home wrote:

Just now :)
Dug out the boiler installation and specification book (left by the fitter) and it states that the initial pressure of the expansion vessel is 0.75 bar*. When I hooked up the pump it read 0.50 bar.
I opened a bleed valve on the highest rad with a bucket underneath, and re pressurized to 0.80 bar. Closed bleed valve, and refilled with water to c. 1.5 bar.
Let's see if there is water in the relief valve in a few days.
Of course, now I have done this, May will get back on track, and we won't need the heating till October :)
*I seemed to find loads of US sites that detail this in psi, and Fahrenheit
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On 17/05/17 11:56, GB wrote:

disconnect from boiler and strain it.
Copper doesn't mind strain.
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On 17/05/17 11:56, GB wrote:

Hacksaw is fine - if you're soldering or using compression, a perfectly square end is not necessary.
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On Wed, 17 May 2017 12:24:45 +0100, Tim Watts wrote:

Ah, TX ..
I'm probably a tad anal about wanting a perfect square cut. Maybe too much reading about pushfit connectors. (I already know that copper is preferred close to the boiler).
One of the most amusing threads I read on this newsgroup was ages ago ... probably an old-school troll. They insisted that the reason their pushfit was leaking had nothing to do with the fact that they had ignored every single directive in the instructions about not using a hacksaw ....
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On Wed, 17 May 2017 11:25:05 +0000, Jethro_uk wrote:

The famous Drivel hacksaw...
One of the tiny pipe cutters would fit, with a push.
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On 5/17/2017 12:43 PM, Bob Eager wrote:

Yes, the clip-on type are a very worthwhile addition to any toolbox!
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On 17/05/17 12:25, Jethro_uk wrote:

Not just preferred - mandated usually withing about 600-1000mm of the boiler - you have to check the manufacturer's instructions :)
Yes, pushfit needs a rounded square cut, so pipe cutter. Nothing else cares - but compression would prefer you had no deep scratches where the olive is.

aka Dribble/Dr Evil
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