The house here at Arborlon has a somewhat primitive grey water system. Water from the bathroom sink, kitchen sink, and shower drains to a grey water reservoir just outside the house in our back yard. it is a small-ish concrete tank set in the ground. It has a submersible dirty water pump that runs intermittently, and the outlet is just a grey water pipe extended down the hill below the house.
We have a second solar panel/battery system we purchased to give us additional power, and it required a new home once we arrived to protect the Switchboard, Inverter, Controller and Batteries.
So we built a box to house it all.