Coupling to HW cylinder coil

I would like to increase the size of my initial radiator pipe to 22mm; to do this I have to replace the ancient fitting on my H/W cylinder, and I'm a bit nervous.
There is what looks like a 28mm, more likely 1 1/8" stub comimg out of a compression fitting that appears to be screwed in to the cylinder.
Could anyone tell me how to make this into a 22mm stub that I can plumb away from; I guess I'll need to replace whatever fitting screws into the tank, but I don't want to undo things I can't do up again !
Or will I need a new cylinder..... next year?
I'd be grateful for any help
mike r
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Use a 28mm to 22mm reducing coupler to the existing 28mm pipework stub. Also, make sure you have indentified all the correct pipework into the cylinder.
Christian.
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be 1" from its age, but it looks bigger than that to me, (I can only see about 1/2" of it)
And isn't 28mm considerably bigger than 1"? So are they compatible at all? Could I just use a new olive?
Or the compression fitting that holds the stub seems to screw into the cylinder, like a radiator fitting - would that have to be replaced, if so from where?
I don't really know what fittings to even look for, but all my 7 (now) rads are being driven through 1 15mm (1/2"?) pipe and it would be fairly simple to improve if I can change the tank fitting.
Or is there a source of knowledge - I've tried the faqs and googled, but not got any answers on this.
TIA
mike r
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On Wed, 20 Aug 2003 18:29:41 +0000 (UTC), mike ring

You could try the Copper Development Association. I believe that their web site has documents with tables of actual outside diameters. You would either need a vernier caliper or perhaps a piece of thread run round the pipe (then divide by pi) to get an accurate dimension. Some of the imperial and metric sizes are fairly close.
In some cases you can transition with fittings, or different olives.
If your cylinder is of an age where the pipework was still imperial, it may be nearing the end of its useful life, so if you are going to do surgery, a backup plan would be prudent. This is not a job to start after lunch on a Sunday......
.andy
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There's probably little point replacing the cylinder connection with more than 15mm pipe. This is because if the cylinder is old enough for imperial connections, the heating coil will be so low spec that it couldn't use the additional heat transfer provided by the 22mm pipe. The reason the connections are so large is because decades ago, installations were done using gravity circulation of the water, which requires large unobstructed passages. With a fully pumped system, 15mm is all you need. When you finally replace the cylinder, you can then upgrade to 22mm, which may actually be beneficial with a modern rapid recovery cylinder.
Christian.
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mike ring wrote:

I'd be really surprised if the coil conection was anything other than 1" BSP male. The fitting that connects these usually have a brass back nut holding a copper cone coupling into the coil pipe. The fitting then is a 28mm or 22mm socket suitable for soldering in a pipe or reducing fitting.
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