Hi well what you will need is a reservoir to store the water that is pumped out. and using a pipe connected
from the outlet of the machine, and going into the tank, through, perhaps on a float valve, in case it ever got too full?
Then, another pipe would then be used, this then to this would be connected a sump pump, that would then pump the water
out of the reservoir and to the inlet side of the WM, here, you will need back flow valves installed so the water from the main input, doesn't go into the reservoir, and water from the reservoir pump, will not flow back along the main feed in, you would have a Y joint here. feeding water back into the machine as required, here also if desired one could have isolation valves to cut off the main water
in, and the feed from the machine's reservoir.
It maybe that one would not need a pump, if gravity, and the pressure were right, but a small bilge pump working off 12V solar cell Battery etc, or whatever should be fine, or even a wind driven pump.
I include a rough diagram to give you the idea.
