Yes, the locker has to be open or the hose gets pinched. It's not ideal, but no new hole in the deck. I don't use the original washdown nozzle at the bow roller at all. When single handing I tie the nozzle on the rail while I go to the cockpit to turn the pump on. It's a powerful jet that is like a big spitting snake when loose on the deck.
Once an inexperienced crew accidentally turned the pump on when cleaning by the helm. By the time I discovered it, the bow lockers were almost full of sea water! But the boat was on the waterline for the first time ever!
