mgb74 had what i thought was a good idea... also, the way i built the sink, i used the plumbing from the washer for the my sink... I attached a y adapter to split the water that was going into the washer into a second hose...

http://www.amazon.com/Orbit-58248-Ga.../dp/B000YDVRH8

when i'm in the darkroom, the open up the water to the darkroom hose , and then in the darkroom sink i have the same y adapter, so that i can turn the water on and off to the sink, these are just attached to 1/2 inch pond tubing so that i can have a 'movable/directional' spout. i would have both y adapters so that i can regulate flow easily...

with this in mind, i don't know if you need a darkroom sink, or just a container which you could place over your sink, with a hole drilled to it, so that it drains into the sink. then just clamp down the the hose onto the side of the container while doing darkroom work.