"crocobaura;c-18249154" wrote:
If you add a dishwasher to the kitchen they will stop using the bathroom sink to wash dishes. As for washing hands after using the toilet, they always wash their hands in the sink in the bathroom they are in, never had them travel between bathrooms to wash hands, let alone go on different floors to do that. Sometimes they might prefer to use the toilet upstairs instead of the one downstairs, but they will wash their hands there as well.
Since the latest patch my Sims go downstairs to wash their hands. The OP is 100 % right.