Feng Shui started off as a science.
It's a lot like urban planning but on a micro-scale.
The example of the fountain really derives from building your home near an underground spring ie a convenient source of potable water. The simple rational is that you don't have to worry about flooding or droughts, spring water is less likely to get contaminated, full of minerals etc. Feng Shui dictates this is good.
This has since become mysticized and mis-applied to modern day apartments as requiring a small water feature.
But like most knowledge passing beyond a certain point where it is easily comprehensible by the masses, Feng Shui has been granted a certain degree of mysticism mostly by it's practicioners who do not understand it and practice it by route and who then try to find ways to explain it to the "common" man.
