Cold water feed round soil stack

I'm a reasonably competent DIYer.

Pic shows current configuration of toilet in downstairs cloakroom.

We are planning a refit with all new fittings, decor, etc.

Obvs, but soil stack is in right hand corner. I'm going to box-in new cistern to hide soil pipe from loo and install a back-to-wall pedestal.

As shown in blue on pic, the current cold water feed runs from other end of cloakroom, behind low level boxing (this will be replaced during refit - height to be decided) and round outside of soil stack box.

I'd like to hide the feed by routing it through the soil stack box.

I suppose the easy way would be to cut a large hole in the soil stack so that I could easily bend some plastic pipe round the back of the soil pipe then box back in, but can anyone suggest an alternative method which minimises the amount which needs to be cut out - ideally limiting it to holes not much bigger than the pipe diameter?

Can't see your pic - is it this one?

https://www.diynot.com/diy/media/loo.103880/

Assuming madrab's pic is indeed your setup- remove the ply (or whatever) boxing, run water pipe behind the stack and round to the loo. Replace boxing with additional cutouts for water pipe. Or were you planning to leave the boxing intact.....that'll make life difficult for yourself

It is that pic and oldbutnotdead you have confirmed my suspicions.

Looks like I'm going to be ripping the room apart anyway, so tearing down a bit of ply isn't going to make much difference.

Thanks for the replies.

You may find it easier to do in copper- the bend radius round the stackpipe may be a bit tight for plastic & putting a plastic elbow in there would be best avoided. Whatever you do it'll be lots easier with the boxing out of the way (there's probably bits of 2 x 2 fixed to the wall in the way of where you want your cold pipe as well)

Just use a cold former, that'll give you the radius you'll need if you're using plastic.