Just a quick suggestion. I think a drain / sewage system would be pretty cool, since right now you connect drain, toilet and drinking (showering etc) all together. It'd be nice, add some moar realism to the game.
Example; you make a drainage system (like water in utilities) and then connect it to toilets and drains (perhaps sinks too because they water has to come somewhere down)...
Nothing too big, would be nice to have.
- TH.
