When I had the piping of my house redone, they left most of the old pipe for cold water in the wall. This is a 18mm steel pipe which runs vertically through (almost) three storeys.
Currently, I am redoing the top storey and strongly believe it is a good idea to have electricity, ethernet and TV up there. Laying cables inside the wall is tedious and now I'm looking at this old unused pipe, which could fit a couple of cables easily.
However, I have sort of a bad feeling at the idea of putting a 230V AC power cable inside a (roughly) 5m long straight steel pipe. School was a long time ago, but I still think I would be building a quite formidable electromagnet, wouldn't I?
In this case I think it would be better to ground (add ground to?) the pipe, put only ethernet and TV inside the pipe and have the power cable outside of the pipe.
How correct or incorrect am I with my assessments? Is it at all wise to use a steel pipe to house any sort of cables?