eli5 Is there a reason the waste water like from showers can’t be filtered through pipes and used for toilet water?

Question

eli5 Is there a reason the waste water like from showers can’t be filtered through pipes and used for toilet water?

In: 797

Answer 1

Some Japanese toilets, upon flushing, refill the tank through a sink basin located on top of the toilet. Wash your hands immediately on flushing with water that goes to the toilet.