Pipework vertically down a wall

[moby_wan]

Hi,

I am running some new pipework to a new shower, the pipework needs to drop from the attic, into a stud wall, but my problem is there is a small amount of block wall above the stud wall.

I want all the pipework hidden in the wall, the part in the stud wall will not be a problem, I realise I am going to have to cut a chase for the section that drops down through the small amount of wall.

But is there a special type of ducting I need for pipework or will any old ducting be ok??? The pipework is 22mm OD, what diameter ducting should I use, to allow for expanding and contracting?????

Thanks in advance!

 

[keego]

I always use a piece of 28mm copper as a sleeve for 22mm.

 

[moby_wan]

Thanks!