Have you ever seen the water tank in your home building?
Hong Kong people are generally living in a residential tower. The water supplied to your apartment is firstly stored in a huge water tank in the top roof of the building by pumping from the underground water pipe. Therefore, the water can be contaminated easily during delivery and the impurities like the rust dissolved from piping and container, chlorine, VOC, etc. can be found in the water.
Rusting can be severe in the water tank and the piping as photos shown. The photos were taken from a 4-5 years old residential building. When you use the water for either drinking or cooking at home, the rust and other contaminants are flowed into your cooking water and then get into your body during drinking and eating. Those contaiminants will harm your body if you take them daily.
Those contaminants cannot be removed by boiling unless special material filtration is used (such as activated carbon) or other scientific methods, for instance, distillation. Therefore, an effective water treatment device is necessary. Otherwise, daily drinking of polluted water can accumulate those contaminants in your body to ruin your health slowly in the long run.