instead of connecting the reel to a pump, connect it to the green python venturi device attached to the sink. once drained, swap the reel to be connected to a pump in the mixing bin (note that the old tank water will be left in the hose and sent back to the tank)
if you dont want to fuss with moving connection to the reel, T it off and put two ball valves on each run, one to the mixing station pump, one to the python venturi. now its as simple as closing/opening the right valves for draining/filling
