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?

--
Timothy Murphy
gayleard /at/ eircom.net
School of Mathematics, Trinity College, Dublin