Extend copper pipe using existing compression fitting

ThisIsWeird

Keep_pedalling said:

ThisIsWeird said:

I'd recommend getting a small tin of Fernox Hawk White (or similar) - a jointing compound - especially for when existing fittings are being reused.

When you dismantle the old, clean it up and give it a smear - over the olive, and also on the male thread. That will both help seal against any leaks, but will also lubricate the fitting and make doing it up a much nicer experience.

(Also use it on the new ends. Just a smear.)

That should not be used on plumbing associated with drinking water.

Thank you - updated.

ThisIsWeird

TheGreenFrog said:

Attached is a photo of the exsting pipe fitting

You use the method you are most happy with. Cutting these pipes and fitting completely new couplers is a good call.

Adding a new compression fitting to that existing fitting without dismantling it is not straight-forward, as that open end is almost certainly not designed to accept a pipe and olive. So you'd first need a 3/4 adaptor, and then some means of adding the 22mm coupler. I guess there are suitable fittings, but who the heck would want to go that way!

Your options are to undo the pipe's remaining nut to expose the old olive and nut and reuse them straight on to a new coupler body, or to cut the pipe as you suggested and use a completely new coupler. I would not - for a novice - entertain trying to remove and replace the olive and nut on that pipe end, as it's easy to score or distort the pipe when removing olives.

If you are really uncomfortable with compression fittings in general - and for a novice it is hard to judge what is tight 'enough', and what could be 'too' tight! - then give some thought to using a plastic push-fit. Provided you cut the pipe using a rotary pipe cutter, so it leaves a nicely rounded edge on the pipe with zero risk of damaging the rubber O ring, then push-fits are hugely reliable. 

danrv

Agree, best to reuse that nut and olive from the old compression fitting. The pipe doesn't look like it's in an easy place to cut.

TheGreenFrog

All the advice was very useful.  I managed to take off the fitting - space was tight and my adjustables would not fit but a quick visit to ToolStation produced a split ring compression spanner.  Amazing tool!  I then tapped off the olives using the adjustable as suggested by @nofoollikeold, cleaned the pipes and fitted new couplers. The olives came off easily so I don't think I distorted the pipes.   

ThisIsWeird

Nice job - well done.

If the olives came off fairly easily, you were lucky, and they clearly hadn't been over-tightened before.

Gavin83

While you can't use hawk white for potable water Fernox do offer such a version called Water Hawk. You can buy it at Screwfix: https://www.screwfix.com/p/fernox-jointing-compound-400g/21548