On 19/11/2015 15:21, Timothy Murphy wrote:
I'm trying to replace the water input valve
on the side of my ceramic WC cistern.
The problem is that I cannot undo the join
(outside the cistern) where the short plastic pipe
from the input valve screws or is glued into a copper/brass fitting
on the copper pipe bringing in the water supply:

http://s1027.photobucket.com/user/gayleard/media/DiY/WCinletvalve_zpsfnzberxz.jpg.html

(Not sure if I have this right - it is my first dip into photobucket.
Any advice on this most welcome.)

Is the plastic pipe likely to be glued into the copper pipe?
If so, do I need to cut through it?


It look to me as if the wrong sort of brass fitting has been used. I'm
pretty sure that you've got one of these:
http://www.fwb.co.uk/pipeline-fittin...sion-fittings-
whereas you should have one of these:
http://www.homebase.co.uk/en/homebas...---05in-157987

With the proper tap connector, the nut which screws onto the ball
valve's inlet pipe rotates on its shaft, and a spigot fits inside the
ball valve pipe, and a seal is made with a fibre washer.

With the wrong sort, the female threaded part is integral with the
elbow, and cannot be rotated independently. This would be a bodge, and
would probably have been sealed with PTFE tape or goo of some sort. The
only way to unscrew this would be to disconnect the compression joint at
the bottom first, and then rotate the whole fitting.

But since you're replacing the valve anyway, it will be easiest just to
saw through the valve inlet pipe and then disconnect the compression
joint. Then replace the ball valve *and* fit a proper bent tap connector
in place of the existing elbow. [If you're lucky, the existing olive and
compression nut may fit the new fitting - and can be re-used without
disturbing the olive,]
--
Cheers,
Roger
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