There's no required age. I think it depends on your kiddo! If you have an ambitious toddler or preschooler, why not let them at it? Just be judicious in what you put out there (avoid breakables & heavily soiled items) and keep track of what they cleaned (you likely will need to rewash--or at least rinse!--what they wash.)
At this point, my 9 year old does a great job with hand-washing. It's truly a help. She has been washing at this "level" (not needing supervision, actually doing the job) for awhile. I never decided to "assign" this to her so I don't know the specific age; she just had the inclination and expressed an interest in helping that way.
I have two five-year-olds who started washing dishes as preschoolers. One in particular is game to wash and actually does pretty well. We have small-sized gloves for them all.
Kids enjoy contributing and feeling competent. And washing dishes is a really satisfying activity.
at 6:34 PM on Dec. 3, 2013