Connecting to old 1/2" copper

Cultivate5970 · Aug 19, 2025

Well I've managed to run into a bit of a pickle by cutting out some old pipework in the loft and realising nothing I had would fit on to the old 1/2" copper pipe up there. Long story short (happy to add details if anyone's interested), I got the sinking feeling when the solder fittings I had wouldn't fit on, so tried compression and couldn't even get the nut on, let alone the olive. Won't go all the way into a Speedfit either.

Just to be clear this isn't the regular 1/2 which is more or less the same OD, and nor will it go on with a bit of a shove, it's not even close to fitting. Measured with calipers, it's about 15.5mm OD.

I've tried buying a bunch of 15 to 1/2 adapters but they mostly just seem like overpriced 15mm couplers, some are marginally bigger on the inch side measured with calipers (like 15.1mm) but still not close to fitting.

Looking around online I've seen references to 'council copper' or 'rhodesian copper' from pre-1970's era which is entirely possible given the age of the property, but I've not really found a proper solution.

Options I've found which seem reasonable but unsure of:
Annealing and swaging the pipe (assuming swaging such a thick walled pipe could be... fun, in the cramped working area)
Philmac UTC coupler (seems possibly best option but not sure if it's suitable for internal use?)
John Guest NC471 (I have one, but not convinced it's the correct size, seems possibly too big, not sure exact dimensions it's designed for).

Any advice would be very much appreciated.
Thanks for reading!

ShaunCorbs · Aug 19, 2025

Easiest way is to file and then Emory cloth the copper or if your good enough use a grinder carefully

As the copper is thick wall you will be fine taking .25 off

Rtplumb · Aug 20, 2025

Cultivate5970 said:
Well I've managed to run into a bit of a pickle by cutting out some old pipework in the loft and realising nothing I had would fit on to the old 1/2" copper pipe up there. Long story short (happy to add details if anyone's interested), I got the sinking feeling when the solder fittings I had wouldn't fit on, so tried compression and couldn't even get the nut on, let alone the olive. Won't go all the way into a Speedfit either.

Just to be clear this isn't the regular 1/2 which is more or less the same OD, and nor will it go on with a bit of a shove, it's not even close to fitting. Measured with calipers, it's about 15.5mm OD.

I've tried buying a bunch of 15 to 1/2 adapters but they mostly just seem like overpriced 15mm couplers, some are marginally bigger on the inch side measured with calipers (like 15.1mm) but still not close to fitting.

Looking around online I've seen references to 'council copper' or 'rhodesian copper' from pre-1970's era which is entirely possible given the age of the property, but I've not really found a proper solution.

Options I've found which seem reasonable but unsure of:
Annealing and swaging the pipe (assuming swaging such a thick walled pipe could be... fun, in the cramped working area)
Philmac UTC coupler (seems possibly best option but not sure if it's suitable for internal use?)
John Guest NC471 (I have one, but not convinced it's the correct size, seems possibly too big, not sure exact dimensions it's designed for).

Any advice would be very much appreciated.
Thanks for reading!

Now, if my memory serves me right, isn’t there a black plastic fitting you can get from a stockist of your choice, that fits any pipe from 3/4” to 15mm. It’s a bit bulky but out of the way in an attic it should be ok. I’ve only used one once and I can’t remember the name of it but one pulled me out of a difficult situation.

Chuck · Aug 20, 2025

Cultivate5970 said:
I've tried buying a bunch of 15 to 1/2 adapters but they mostly just seem like overpriced 15mm couplers, some are marginally bigger on the inch side measured with calipers (like 15.1mm) but still not close to fitting.

BS 659 1/2" tube had a maximum o/d was specified as 0.596" or 15.14mm.

American '1/2" copper' has an o/d of 5/8" or 15.88 mm and comes in about three wall thicknesses. I suspect this maybe what you've got.

You might try making your own capillary fitting by using some good quality new 15mm pipe and expanding it up with a 5/8" 'copper pipe expander drill bit'.

Cultivate5970 · Aug 20, 2025

Thanks for all the replies, they're much appreciated.

ShaunCorbs said:
Easiest way is to file and then Emory cloth the copper or if your good enough use a grinder carefully

As the copper is thick wall you will be fine taking .25 off

This might be a good option as I think I would be most comfortable with it being soldered or a compression fitting longer-term. But might have to keep some backup options just in case I muck it up.

Rtplumb said:
Now, if my memory serves me right, isn’t there a black plastic fitting you can get from a stockist of your choice, that fits any pipe from 3/4” to 15mm. It’s a bit bulky but out of the way in an attic it should be ok. I’ve only used one once and I can’t remember the name of it but one pulled me out of a difficult situation.

Is that the Philmac one? That one does look to be a strong contender but I was a bit concerned that I saw a caution on what appears to be their American distributor saying it's not for interior use. But suspect it could be some national approval nonsense, and that it's not suitable for hot water. It's only for mains cold water in my case, thankfully!

Chuck said:
BS 659 1/2" tube had a maximum o/d was specified as 0.596" or 15.14mm.

American '1/2" copper' has an o/d of 5/8" or 15.88 mm and comes in about three wall thicknesses. I suspect this maybe what you've got.

You might try making your own capillary fitting by using some good quality new 15mm pipe and expanding it up with a 5/8" 'copper pipe expander drill bit'.

I don't think it's either of those which is why I think it's been such a problem. It's definitely around 15.5mm, not as big as 15.88 but bigger than 15.14 to not fit it any 1/2" adapters couplings. It's also quite consistently that size and doesn't appear to be oval so not just freeze-swelled as other places suggested. My research didn't find much apart from those references to "Rhodesian" or "council" copper on the Internet. The guys in my local plumbing counter didn't know what to suggest, and a plumber in the shop joining in seemed to think it was regular 1/2 and it would just be a bit snug in a 15mm. Wish he was right!

I did wonder about borrowing a pipe expander and stretching a regular end-feed fitting out a bit, since they're a bit sturdier and don't have as far to stretch. Might have a play with both.

I do have one of John Guest's imperial to metric adapters (part NC471) which has markings for 5/8 on it, but I'm concerned my 15.5 isn't quite big enough to ensure a good seal long-term. It's wide enough that it leaks like a sieve on 15mm on a pressure tester. I did email JG for technical details but heard nothing back yet.

Reason for not just trying it, is a plumber did manage to force on a Speedfit but I would prefer a more permanent solution as I'm concerned it's not fully into the fitting (the inner body of the Speedfit is narrower than this pipe). Paranoid? Probably, but mains pressure water does worry me, especially high up! Sadly, I didn't have the foresight to chop off enough of the pipe to test it away from the live installation. And don't want to knock off a working-for-now solution and fit something that might not fit. It was a right effort getting the Speedfit on once!

Cultivate5970 · Aug 21, 2025

Caliper measuring pipe for those interested. Walls look a bit thicker than they really are as it was cut with a pipe slice.

Rtplumb · Aug 21, 2025

Cultivate5970 said:
Thanks for all the replies, they're much appreciated.

This might be a good option as I think I would be most comfortable with it being soldered or a compression fitting longer-term. But might have to keep some backup options just in case I muck it up.

Is that the Philmac one? That one does look to be a strong contender but I was a bit concerned that I saw a caution on what appears to be their American distributor saying it's not for interior use. But suspect it could be some national approval nonsense, and that it's not suitable for hot water. It's only for mains cold water in my case, thankfully!

I don't think it's either of those which is why I think it's been such a problem. It's definitely around 15.5mm, not as big as 15.88 but bigger than 15.14 to not fit it any 1/2" adapters couplings. It's also quite consistently that size and doesn't appear to be oval so not just freeze-swelled as other places suggested. My research didn't find much apart from those references to "Rhodesian" or "council" copper on the Internet. The guys in my local plumbing counter didn't know what to suggest, and a plumber in the shop joining in seemed to think it was regular 1/2 and it would just be a bit snug in a 15mm. Wish he was right!

I did wonder about borrowing a pipe expander and stretching a regular end-feed fitting out a bit, since they're a bit sturdier and don't have as far to stretch. Might have a play with both.

I do have one of John Guest's imperial to metric adapters (part NC471) which has markings for 5/8 on it, but I'm concerned my 15.5 isn't quite big enough to ensure a good seal long-term. It's wide enough that it leaks like a sieve on 15mm on a pressure tester. I did email JG for technical details but heard nothing back yet.

Reason for not just trying it, is a plumber did manage to force on a Speedfit but I would prefer a more permanent solution as I'm concerned it's not fully into the fitting (the inner body of the Speedfit is narrower than this pipe). Paranoid? Probably, but mains pressure water does worry me, especially high up! Sadly, I didn't have the foresight to chop off enough of the pipe to test it away from the live installation. And don't want to knock off a working-for-now solution and fit something that might not fit. It was a right effort getting the Speedfit on once.

Transition fittings where the ones I was thinking of and they're made in brass or plastic.

Vip1969 · Aug 21, 2025

Just file the 1/2" pipe with a good hand file all round the pipe. It will take time but just be patient. If you are not eperienced don't use power tools. I had to do the same a few years ago with an old 1" copper pipe which I had to solder to 28mm end feed - it took me nearly 3 hours of patiently filing! I could not any use power tools because the pipe was very close to a wall. With 1/2", it should take less than 1 hour.

Rtplumb · Aug 22, 2025

Rtplumb said:
Transition fittings where the ones I was thinking of and they're made in brass or plastic.

Just an add on, you do know that you can also get imperial to metric end feed fittings? 1/2 to 15 mm etc? They should fit and no filing down.

Cultivate5970 · Aug 22, 2025

Rtplumb said:
Just an add on, you do know that you can also get imperial to metric end feed fittings? 1/2 to 15 mm etc? They should fit and no filing down.

Yep, I've tried several different ones, none fit. Not even close. Some just seem to be overpriced 15mm fittings, others are a tenth or two of a mm wider, but none I've tried have been 15.5mm ID.

It's an odd size of pipe, don't think the local plumbing supplier believed me until I took in a small offcut to show them.

snowhead · Aug 22, 2025

Does the remaining pipe go back to a screwed fitting that you could join on to with a new 15mm fitting and pipe?
What was on the end of pipe you cut off, was it soldered or mechanical?

Chuck · Aug 22, 2025

Cultivate5970 said:
Yep, I've tried several different ones, none fit. Not even close. Some just seem to be overpriced 15mm fittings, others are a tenth or two of a mm wider, but none I've tried have been 15.5mm ID.

Don't forget that for a capillary fitting to work correctly there needs to be a gap of ca 0.1mm (i.e. 0.2mm on diameter) for the solder to be drawn into. So, if your measurement s are correct, you're looking for a fitting with a 15.7mm id.

Cultivate5970 · Aug 22, 2025

snowhead said:
Does the remaining pipe go back to a screwed fitting that you could join on to with a new 15mm fitting and pipe?
What was on the end of pipe you cut off, was it soldered or mechanical?

Sadly it disappears into the floor after a bend. I think the next joint below is an old style compression fitting (swaged type perhaps?)

I had cut off an old 15mm compression isolation valve which it looks like had been fitted with some filing and swearing. From the markings on the copper it looks like the back nut had been hammered on and it was TIGHT against the pipe. I never thought to check the diameter before cutting either side of the old valve. We live and learn! The other side is regular 1/2 so no issues there.

Chuck said:
Don't forget that for a capillary fitting to work correctly there needs to be a gap of ca 0.1mm (i.e. 0.2mm on diameter) for the solder to be drawn into. So, if your measurement s are correct, you're looking for a fitting with a 15.7mm id.

Good point, got it!

chrisW50450 · Monday at 10:10 AM

Cultivate5970 said:
Well I've managed to run into a bit of a pickle by cutting out some old pipework in the loft and realising nothing I had would fit on to the old 1/2" copper pipe up there. Long story short (happy to add details if anyone's interested), I got the sinking feeling when the solder fittings I had wouldn't fit on, so tried compression and couldn't even get the nut on, let alone the olive. Won't go all the way into a Speedfit either.

Just to be clear this isn't the regular 1/2 which is more or less the same OD, and nor will it go on with a bit of a shove, it's not even close to fitting. Measured with calipers, it's about 15.5mm OD.

I've tried buying a bunch of 15 to 1/2 adapters but they mostly just seem like overpriced 15mm couplers, some are marginally bigger on the inch side measured with calipers (like 15.1mm) but still not close to fitting.

Looking around online I've seen references to 'council copper' or 'rhodesian copper' from pre-1970's era which is entirely possible given the age of the property, but I've not really found a proper solution.

Options I've found which seem reasonable but unsure of:
Annealing and swaging the pipe (assuming swaging such a thick walled pipe could be... fun, in the cramped working area)
Philmac UTC coupler (seems possibly best option but not sure if it's suitable for internal use?)
John Guest NC471 (I have one, but not convinced it's the correct size, seems possibly too big, not sure exact dimensions it's designed for).

Any advice would be very much appreciated.
Thanks for reading!

As it is in a loft it may have been expanded a bit by freezing. Measure the pipe a bit further back with your vernier gauge. You may find it will be OK.

Old 1/2" copper was only slightly larger than 15mm. Conex fittings always had enough play for them to fit, some of the italian brassware was much tighter.

Cultivate5970 · Thursday at 12:30 AM

I've not had a chance to get back up yet but I will have another check when I do. I did measure it a bit further back and it seemed quite consistent but I'll measure as close to the floor as I can and see if it's any different.

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Connecting to old 1/2" copper

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