Tap water quality?

Water is supplied to houses and flats by pipes or water tankers through taps.Most water is acquired through desalination of sea water.Although desalinated water looks clean and clear but still is not drinkable quality. I have noticed it is full of rust
as my r.o filter shows and salt. This filter has 4 stage cleaning. here is the picture of one used filter out of this r.o filter.

Most third world countries poorly paid workers rely on drinking water tanks "Maa es sabeels" which are everywhere in the Kuwait or tapes in their flats.They are unable to afford bottled water. petrol is cheaper than bottled water and bottled water is affordable for locals and westerners.