I know this is a bit of an older thread, but I just had this problem, and I was trying for a while to get my dupe to wash his hands when passing by the wash basin. I tried making it bi-directional, I tried "Move to" several times, and nothing. I was just about to restart the game when I noticed something, the basin tubes on the side - where you can see the blue (clean) and green (dirty) water, they were empty.
Should look like this:
But instead looked like this:
So clicking on the properties of the basin, I looked at the "Contents" and found this:
I then realized that I had a priority of 5 on the basins, so they hadn't added water to them. I upped it to 9, and immediately someone went and got water, now I see this:
And then my dupe immediately washed his hands as he passed by the basin. It didn't say it needed any materials (much like a research station says it's waiting on water or dirt, or an oxydizer waits on algae) so I didn't realize they were dry.
Hope that helps.