I have to take hot & cold supplies to an en-suite in an extension. The kitchen is the closest point to intercept supplies (also rising main supply if req.). I need to know if the supply's must come in under the floor or is it possible to route pipe's from the loft space in the original build over to the new build or will this cause air to trap in the pipe? Also, what bore of supply should I use (15mm or 22mm). A standard mixer shower is to be used. I'm not a plumber but want to give it a go as I am handy with most things. Just like to know from people in the know before moving on. Thanks in advance for any advice.