I could have several different z values along the line, and currently the expression would only allow me to create one z value for the whole line.
I am stressing currently, because it would be great if you could create an expression where the 'attribute' that was actually the geometry and some type of expression against it, therefore altering the z values at each point.
The anchor preset would be the perfect answer but I can't say I have thought about any details that may negate the use of it.
Like you say, I could recalculate the z value to make the z value the centre of the pipe but I was hoping to do it dynamically, as many system use this data, so we would have to extract it from the data source and apply the change just for our own purposes. I am more keen to be able to work with the original data source of course.
Thanks
Below is an image where you can see the pipe extend beyond the bottom of the manhole, when in reality it is actually just above the bottom of the manhole.