The first and easiest step to identifying problems (opportunities!) for sinks seemed to be making a bug list. Obviously, the easiest way is not always the best way, and a bug list is limited to problems relevant to me, but I thought I'd let loose with Occam's Razor and hopefully find a few good points to branch off from.
Okay, so the bug list does its job. Lots of simple, irritating little things that happen often - mainly with bathroom or kitchen sinks. What I didn't really get out of it are: things that happen with less frequent situations (laundry tub, hand-washing clothes, pools, dish basins like they have at restaurants, industrial dishwashers), things that are perhaps more fun than functional (LED water faucets), and technical details (materials, assemblies, water pressure).
Since the assignment was to focus on one area, I stuck with the direction my bug list took: household sinks (kitchen and bathroom) and related tasks. I think fun things can fit into that category, as it relates to how kids approach mundane household activities.
Since I'm not a kid, I needed to figure out what kids might want or need in their daily routine. Time to create a persona. I asked a few friends who study or work in early childhood education for tips on what kids are into these days. Although I think solutions in this area might lean towards younger kids just learning good hygiene habits, I included a larger age range (3-13) at the "problems and opportunities" stage in case some other ideas come from it (a line of sink-related prank products for older kids?).
Again, this persona board is more broad than it would be if I were working on a solution, and basically gives an overview of what kids within the age range are into, as well as some products that have been marketed towards those ages.
For my third method of investigation, I thought I'd revisit the more refined concept of daily routine, and storyboard how some of the bug list items fit into the bigger picture.
I have photos to go with the storyboard that I'll upload as soon as I can get this stupid borrowed digital camera working (i.e., find a card reader because this adapter cord is shot).