How do I join a new copper pipe onto an old one, when they're slightly different sizes?
The old one is probably an Imperial width and the new one is a standard 15mm.

I'm probably going to end up replacing all the old pipes with new ones, aren't I? Bummer.
(Juan Quar is clinging to her front teeth on, Sun 2 Jun 2013, 9:09, 20 replies)

Normally old half inch copper and new 15mm copper are the same size and can be joined with any 15mm solder or compression fitting.
On rare occassions there is a rogue old half inch copper that is very slightly bigger. I've only come across it twice in 25 years but a good plumbers merchants will stock a compression fitting that will join the two sizes no problem.
Good luck
(boarders You won't catch me with my trousers, Sun 2 Jun 2013, 9:18, closed)

It's definitely just that bit too big, it's the original 60 year-old pipework. I'm using compression joints so it's off to B&Q as soon as it opens at 10.
I'll get one of those joints, didn't know there were such things. It'll be easier than dragging out the old piping to replace it all.

Thank you for replying!
(Juan Quar is clinging to her front teeth on, Sun 2 Jun 2013, 9:51, closed)

it is a fairly rare size of pipe so you might struggle at B&Q for the fitting. You're more likely to have success at a specialist plumbers merchant such as Plumb Centre.
Doesn't help a great deal on a sunday i know but you might have to be patient on this one.
Just recalling, i think the fitting is labelled as 15mm to 16mm.
(boarders You won't catch me with my trousers, Sun 2 Jun 2013, 9:59, closed)

Oh 'ell, we do have a Plumb Centre near here but it'll be closed, and I'm working tomorrow morning!
New question: will a ball joint block off the pipe adequately while I use the washing machine which is fed from lower down the pipe? Or am I looking at a stop end until I can get the special joint?
(Juan Quar is clinging to her front teeth on, Sun 2 Jun 2013, 10:02, closed)

Is the pipe you want to cap off 16mm. If it is, then the only way to cap it without a 16mm fitting would be to flatten the pipe then fold the flattened pipe over on itself. Scary bit now. Apply solder to the flattened pipe to seal it off until you can obtain a fitting.
(boarders You won't catch me with my trousers, Sun 2 Jun 2013, 10:20, closed)

Oooh, that's really living on the edge!

(Juan Quar is clinging to her front teeth on, Sun 2 Jun 2013, 16:59, closed)

Do you mean a ball valve?
If so, it should be fine.
You generally find ball joints on a cars steering.
( social hand grenade I was a lurker before you were a lurker, Sun 2 Jun 2013, 19:50, closed)

I knew that
er...
(Juan Quar is clinging to her front teeth on, Tue 4 Jun 2013, 19:43, closed)

Sure it's not just a 22mm? solder ring joints are more reliable than comap fittings for the average DIYer.
EDIT:
*notes the word slightly*
should be able to use a compression fitting
( da5id <YOUR SIG HERE>, Sun 2 Jun 2013, 9:19, closed)

No, it's just a shade too wide for the joint I'm offering it. The nut won't fit.
Compression joints are the way forward for me. I'm too dangerous with a blowtorch. PTFE tape is my god.

Thank you for replying!
(Juan Quar is clinging to her front teeth on, Sun 2 Jun 2013, 9:54, closed)

If it's just the nut that's too tight on the pipe, but you can slip an olive over it and get it into the body of the fitting, it may be that the nut is deformed or badly cast.
(gordonjcp, Sun 2 Jun 2013, 12:15, closed)

No, the olive won't go on either.
You can see the slight difference in size if you compare them closely.
(Juan Quar is clinging to her front teeth on, Sun 2 Jun 2013, 16:56, closed)

if you can not get your nut to fit try dhaving it first. i found that it slips in easyer and a plus point is that hairs dont tangled and make your eyes water when you have finished

( fluffybunnykiller Is feasting on the clitoris of life, Sun 2 Jun 2013, 15:42, closed)

Thank you, I will try dhaving first
but I'll still have to pop to B&Q for a dhaver.
(Juan Quar is clinging to her front teeth on, Sun 2 Jun 2013, 17:00, closed)

This is a proper question, you're doing it wrong!

( Infidel , shit and wrong, Sun 2 Jun 2013, 16:52, closed)

I know, I am deeply ashamed.
I will try to think of an *improper* question.
(Juan Quar is clinging to her front teeth on, Sun 2 Jun 2013, 16:58, closed)

Did you manage to get hold of that fitting

(boarders You won't catch me with my trousers, Tue 4 Jun 2013, 22:56, closed)

No, not had a chance yet, which is lucky really as I will have to replace that length of pipe anyway after finding another split in it further up.
So it's modern 15mm all the way up from today!

After the new pipes go in I'll be lagging them with super-thick insulating stuff so this doesn't happen again. They were lagged before but it seems the insulation was too feeble.
(Juan Quar is clinging to her front teeth on, Wed 5 Jun 2013, 5:57, closed)

Happy days

(boarders You won't catch me with my trousers, Wed 5 Jun 2013, 22:52, closed)

My brother popped round to help. He replaced the up pipe successfully but the cistern still wouldn't fill.
We got repeatedly squirted while testing the lower joints, then took the flush mechanism to pieces and found a tiny piece of grit blocking the inlet. God, we're like Sherlock Holmes, we are.

It all went smoothly after that. I miss those happy times already.
(Juan Quar is clinging to her front teeth on, Thu 6 Jun 2013, 6:56, closed)