I'm in the design stage for building a darkroom. Other than the final wash of the print do you need to have running water? If there will be a bathroom across the hall would that be OK? I could mix up the chemicals needed before hand so they could be in the trays. I already do my B&W/E-6 in the bathroom. I'm just looking to make prints in the darkroom.
A darkroom without running water works, but it's a compromise. If you have running water across the hall, I'd find a way to get warm and cold water, including drainage, into the darkroom. Maybe, it's not the highest priority, but I wouldn't want to be without it for long.