Disinfection is an effective way to kill these microorganisms. According to the Environmental Protection Agency, and other health agencies, chlorine is currently one of the most effective disinfectants to kill harmful microorganisms. Federal and state laws and regulations, including the Safe Drinking Water Act require disinfection of all public water supplies. You may want to use a carbon pour through type filter. There are several on the market, Brita, Pur, and Ametec, to name a few.
Water contains minerals that are left behind when the water is heated or evaporates.
These minerals, as well as the drinking water, are safe. The spots can also be caused by the over use of some dish detergents. The cause of this could be from the disintegration of the dip tube in the hot water heater, as some dip tubes have been known to corrode and fall apart. There is a little known problem that is just starting to become recognized, water heaters made in the 1991-1996 range are particularly susceptible. The remaining dip tube can be remove and replaced.