maybe you missed this bit from my quote:
Chlorine is very abundant in soils,
Plants need it, without chlorine they will die.
I let my water sit out purely for pH stability purposes. When water comes from the tap it will be cold, very cold. Cold water has a higher pH than the same water warmed up. This is why a lot of hydro growers get problems with fluctuating pH. allowing the water to get to the temperature it will be once it is in the res is the best way to keep pH in check. Water has an alkalinity value and this will actually buffer the pH back up.
Some guys will pour straight from the tap add the nutes, measure it and go... this will always lead to raising pH in the res.
Chlorine is pretty crap at killing bacteria, but it's safe for humans. Lots of the bacteria still remains in water with chlorine, but the bacteria is considered to be safe for humans, our stomach acids kill it. However chlorine is absolutely useless at killing the real nasty bacteria like e.coli. e.coli also likes to mutate, piss it off and it mutates. last year it killed 2 million children in the US alone... and things are getting worse.
this is why the US government has suddenly started thinking green... it is believed artificial fertilzation and the destruction of the micro life in farmlands is what has led to e.coli so readily mutating into a killer virus.
anyway, off subject... a little.