I've got the same washer. To properly drain it, you need to tip the thing over, with the drain hose disconnected, so all the water gets out, or it gets pretty funky pretty fast. I don't have a flow meter on mine so I'm not sure what flow rate I get, but I let my water flow through as slowly as possible once the tank is full, then let it run for an hour before removing prints. You just need to be careful to not forget prints in the washer for more than overnight - I once made some prints on a thursday, forgot to pull them out, and went away for the weekend. When I went back in to the darkroom on Monday, well... I had some nice white pieces of paper and a layer of sludge on the bottom of the tank.