What is the dimension of microbore pipe?

Hi. I need to re-pipe a new bathroom radiator (fitted last year) back to a manifold before tiling the floor. At present, the copper pipes from the manifold, which feeds all the upstairs rads are 3/8" (ext dimension by my measurement). I'd been led to understand that I have a microbore system but I've found a few old lengths of pipe in the attic (original use unknown) which I estimate to be only 5/16".

Do these sound like standard measurements and which is microbore?

The original bathroom rad, fed with 3/8" as I've just described, terminated under-floor in a gun-barrel elbow which in turn was connected to gun-barrel coming through the floor and into the rad. When installing the new rad, the plumber cut the gunbarrel over-floor and connected it to 1/2" copper pipe going into the rad.

One or other joints at the elbows have leaked so I'm anxious to get rid of them before tiling. I'd like to install 1/2" Qual-Pex from the rad straight back to the manifold. Can I get a suitable 1/2" to 3/8" connector at the manifold end?

Any advice appreciated.

The larger B&Q stores have plenty of fittings 8mm, 10mm, 14.7mm, 22, 28, 1/2", 3/4" in brass, brass/qualplex, qualplex etc and all the adapters you could think of - Murphy's law might mean they won't have the one you want though. They also have a relatively easy return policy.

In the UK where you see more mircobore they use both 8mm and 10 mm as it depends on the distance of your runs much the same way that we use 1/2", 3/4" and 1" now.

davidoco said:

The larger B&Q stores have plenty of fittings 8mm, 10mm, 14.7mm, 22, 28, 1/2", 3/4" in brass, brass/qualplex, qualplex etc and all the adapters you could think of - Murphy's law might mean they won't have the one you want though. They also have a relatively easy return policy.

In the UK where you see more mircobore they use both 8mm and 10 mm as it depends on the distance of your runs much the same way that we use 1/2", 3/4" and 1" now.

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Thanks Davidoco. Sorry about a very convoluted way of asking a simple question! I was just about to simplify it when I saw your reply. I'll bring samples of the pipes concerned into the store.

Any decent plumbing supplies merchant should also stock what you need and would be a good source of advice should any be required. Often easier go to the DIY sheds and browse through the range on display though.

Thanks Leo. I got the opportunity this morning to drop into the best hardware store in South Dublin and as you say I got both good advice and the necessary bits.