[Holger]

There are discussions ongoing to use the grey water for flushing the WC and for the washing machine. There is a filter in front of course.
When building an new house you can have a second water circuit for that.
I dont know the negative effects. Are the pipes clogged faster? You also have to have a cross-system if the collected water does not suffice and you need to mix in fresh water.
What about the WCs? Do you need to clean them more often? How oftne do you need to clean the filter?

As usual it is all about what is left in my wallet.
Installing such a system costs more then a normal system of course.
How fast can I get a ROI?

And so on.