Replacing CH expansion tank - fitting question

nofoollikeold

The pipe from the boiler is NOT threaded.  If you look at your original photograph, the pipe coming from the boiler has a nut over it, just before it enters the manifold.  If you unscrew this nut it will slide back along the pipe and you will be able to move the expansion vessel to the right.  

ThisIsWeird

nofoollikeold said:

The pipe from the boiler is NOT threaded.  If you look at your original photograph, the pipe coming from the boiler has a nut over it, just before it enters the manifold.  If you unscrew this nut it will slide back along the pipe and you will be able to move the expansion vessel to the right.  

As you say - almost certainly a compression fitting, so there will be an olive on that pipe under the nut. A wee smear of joint compound when refitting should see it watertight again.