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

it can be, it is called grey water, but it means doubling up the number of pipes and making absolutely sure you don’t mix the two. So it rarely makes sense