Pipe Bending

[alanworland]

I have a bit of central heating pipework to undertake shortly and I have a 15mm pipe bender, but I was wondering what might be the tightest radius bend I could pull in annealed copper pipe?
My existing bender manages a 62mm radius bend (on pipe centre line) and I am considering making another, smaller former but thought I would put the question to the wisened forum users rather than waste my time!

[les]

I'm not a heating engineer but would chance to say the 62mm radius is from a standard bender like mine and as such would think that the bend is as tight as it's safe to be without kinking or indeed streching the copper too much. The system i've got includes a certain amount of 8mm insulated copper pipe running behind drylined walls, before returning to 15mm to the rads, the system works well, maybe for tighter bends you could consider a smaller bore.

[Jefftav]

I have done a bit of this in my time and the formers normally give you the best radius. There probably is a safety margin built in but as the previous poster says if you weaken the pipe there maybe consequences later on(Hot water being pumped and a split in your pipe will make a mess). So unless you really need to I wouldn't make the bends any tighter than your existing former allows or look for smaller bore pipe.
Plastic pipe (I forget the trade name) tends to be more forgiving but again if you flatten it whilst bending then throw it away. You can buy adaptors to connect this to copper systems and I have used plastic with reasonable success.

[billlobban]

You have to take care with plastic pipe as despite claims by the manufacturers some of it is not vermin proof - as I know to my cost Eventually my mobile mouse trap caught and ate the afforementioned vermin

[alanworland]

Thanks for your replies - I wanted a bend which was tighter than the bender could pull - but not as tight as a solder bend.
The ideal sort of radius would be the 'swept' 90 degree bend which used to be available, but I don't think you can get them any more - I will probably end up with standard 90 degree bends

[billlobban]

You can still buy 'swept' 90 bends try http://www.bes.co.uk

[alanworland]

Thanks for that billlobban - I thought they were phased out years ago!