I dont have a garden live in a first floor one bed flat, I manage, you just have to be a bit more creative
4040 ro mounted on wall above sub landing window, waste goes out through wall into drain pipe
pure is fed through braided 1/2" hose under floorboards of landing and living room and out through window frame and zip tied to a downpipe to the front door
I connect up 20 meters more hose and feed pure straight into vans tank
theres always a way