Drawing up floorplans and mechanical diagrams?

I want to draw up a detailed set of floorplans. I also want to clearly illustrate where the electrical wiring and plumbing in the house go, both for myself and for future reference for any plumber or electrician I may hire. I'd like to include every outlet and bit of pipe, so that one can see what is on what circuit as well as which pipe is present that is not in use. I'd love to also include the pipe from our old vacuum system, with the hope of using it as a conduit for wiring in the future, but I know that that may be more difficult, given that most of the outlets for the vacuum system have been removed.

This seems like a good time to start working on such a project. I haven't put any insulation up in the attic yet. I have the library ceiling open, which gives me access to a good deal of the plumbing for the two second floor bathrooms.

The best solution I've found so is to just use large format graph paper to draw the floorplan, with a scale of 1"=1'. I plan to use additional sheets to overlay the mechanical systems. While this requires little additional expenditure, it's not as clean as I would like, nor does it allow for easy editing once I've finally inked everything in. Further, short of doing more drawings, it doesn't allow me to show how the plumbing goes vertically through the walls.

The desire to record all this information may seem slightly excessive. Keep in mind that we plan to be in this house for at least the next 30 years, so the knowledge recorded here will build up over time. Given this, perhaps the best way is to just work on paper, as software can change so much.

I welcome any suggestions on the subject.