It's exceedingly unlikely your American home is keeping graywater separate from blackwater. If it were, you would know, it would have been mentioned as it's qu

It's exceedingly unlikely your American home is keeping graywater separate from blackwater. If it were, you would know, it would have been mentioned as it's quite exceptional. California not long ago changed its laws regarding graywater handling in response to the sustained droughts. Now residents are permitted to divert graywater themselves for other purposes like irrigation and gardening. So it's become a little more common to find diverted graywater systems in response to this change, but they're often ad-hoc diy setups in drought-stricken regions. You're right though, showers and laundry are huge wastes of water, at least relative to residential water use. Unlike toilets, they're also much harder/impossible problems to solve without the voluminous use of clean water. With toilets there are options like composting and incinerating, and in places with ocean access seawater can be used for flushing. Bathing and laundry don't really have alternatives.