“I had an old farmhouse where the sink drains went to the large garden as gray water. “
Lots of smart people who have septic tanks drain their washing machine water on the yard or and on the garden. Pointless to waste that much water.
You cannot waste water. You can redistribute it ineffectively, but it does not get chemically eliminated. It is either sent back into the soil, processed in municipal or on site waste treatment facilities, evaporated into the air to be recondensed and return as rain, or emptied into streams, lakes, or oceans.