Connecting Copper pipe to Gun Barrel pipe.

Wavey · 24-10-2008 03:15PM #1

Afternoon all,

I am planning on replacing some radiators in my house.
The old ones are piped with what looks like 3/4" Gun Barrel pipework.

How can I connect this to 15mm copper pipework?

I have googled this but cant find anything.

Any advice appreciated.

Thanks,

Wavey.

bbam · 24-10-2008 04:44PM

Hi..
I used to plumb a bit... I think what you are looking for is a "318" fiting.. Ask at any good hardware store and they will have one...

copper12 · 24-10-2008 09:18PM

spot on

24-10-2008 11:00PM

A 327 would work aswell if you had some 372's for the last pair.

Micky Dolenz · 25-10-2008 12:59PM

Have I missed something? How could I connect GB to copper using a 318 (tee)?

I would unscrew leg from rad, where it goes into GB elbow. I would then screw a 311(3/4 x 1/2 if needed) into the GB elbow and run copper from there to the new radiator valve.

Wavey · 28-10-2008 12:45PM

Thanks for the replies lads.

Where can I purchase these 318 fittings?
I tried B&Q and Woodies over the weekend but they didnt stock them.

I have also looked on the Screwfix direct web site but I couldnt find them there either. Unless they were called something other than 318.

Thanks again,

Wavey.

Pete67 · 28-10-2008 01:04PM

Here you go:

link here

311 or 312 is most likely the fitting you want. Also available as elbows, 316 or 317. Available from any plumbing supplier or good hardware shop.

Wavey · 28-10-2008 02:39PM

Thanks for the lenk Pete.

Although I was under the impression that you needed a special fitting that separates the steel from the copper to prevent corrosion through electrolysis.

THIS site suggests you use what is called a Dielectric Union.

Or is this just overkill?

Also when I measured the existing mild steel pipe it measures 17mm OD. This seems a strange size and is too small to be 3/4" imperial.
Any ideas what size coupling I need to fit onto this threaded pipe?

Thanks again.

Wavey.

Pete67 · 28-10-2008 03:00PM

The dialectric union sounds like a good idea, but I've never used one, or seen one used.

17mm OD steel pipe is probably 3/8" BSP, the threaded portion of which has a major diameter of 0.656in (16.66 mm). The OD of the pipe itself is 17.2mm

It's a standard size.

See here:

Connecting Copper pipe to Gun Barrel pipe.

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