One thing I failed to mention. GIS is only a tool, it doesnt correct mistakes or even allow you to know what data you have is correct or not. IT ALL MUST BE VERIFIED.
Most cities have water system infrastructure that is 50 to 100 years old and in most cases, the water lines and stations arent even located correctly. OR, there may be several instances where many kinds of pipes use one hole (Even though thats a no no). Ive seen where water pipes , all made of old wooden pipes made up like 20 ft pencils would be stuck in the same trench along with gas lines or electric lines. OR, water pipe lines would be mapped to be up to 100 feet off from where they really are. OR , the lines are incorrectly measuredOR, there would be valves incorrectly sized or located.
GIS can only be used as a tool as long as the information stuffed into the mapping system is correct. Remember the old saying 'Garbage I/O' Ive seen where giuys had their GIS maps loaded onto their hand held computers and would do the surveying to dig up the pipes and then miss the pipes by 50 feet. .
The biggest job in infrastructure is to first make the maps correct