With this mod, your Sims will no longer wash dishes in the bathroom if you place the right sinks. The entire time I played this was an issue the entire time. Mods: Wash Dishes Fix by MSQSIMS from TSR. Rearranged the floor plan and made the kitchen/dining area separate from the living room. Added a third sink to the kitchen and still only the occasional single plate would be washed. Same result with dishes either on the desk or on the kitchen counter next to the sink. Then they would put them on the computer desk. Then instead of going to the trash can (in the kitchen) or one of the sinks they would plop them into the bookcase! I used old homework books and a whatever would fit to fill in the empty bookcase slots.
They would go thru the house gathering all.
Sims (different ones even different generations) would go about gathering dirty dishes from the dining area.
There was a sink in the kitchen, one in the downstairs bathroom and one in the upstairs bathroom. The Living Room/Kitchen/Dining area were all open floor plan. In my very recent save this became a big issue especially with Neat trait Sims.