with no shutoff at the bottom ,when you shut this system off upstairs ,all the water in the hose and pvc will still end up in the tank. hope you have some sort of overfill protection in mind.
Close the discharge end of the hose.
drag all the hose upstairs behind you.
turn off the upstairs tap.
open the non-hose side of the splitter.
lift the discharge end up higher than the sink and then open that valve and the water will start draining into the sink.
roll the hose up, always keeping it higher than the sink.
when it is all rolled up to the faucet, close both valves (all valves at this point) and disconnect from the tap.
No muss, and only a little fuss.