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

In some countries it is used. For instance, you can buy toilets with sinks on top of the cistern. Fresh water used to wash your hands becomes “grey water” which is used in the cistern to flush the loo next time.