Do all dishwashers have filters in Whirlpool?

Yes, all modern Whirlpool dishwashers manufactured after 2010 have a filter that needs to be cleaned, but older Whirlpool models had self-cleaning systems without user-removable filter. Modern Whirlpool dishwashers like models WDT730HAMZ, WDT750SAKZ, WDT920SAPZ, WDTA50SAKZ, and WDT505SAKZ have a manual clean filter system located at bottom of tub under lower spray arm that consists of upper coarse filter and lower fine mesh filter that traps food particles to protect pump. This filter must be cleaned every 30 to 60 days to prevent poor cleaning, odor, and drain clogs, and is removed by twisting counterclockwise a quarter turn. Older Whirlpool dishwashers manufactured before 2010 had self-cleaning filter with hard food disposer that grinds food and flushes down drain, similar to garbage disposal, and does not have a user-removable filter that needs regular cleaning, though they are louder. So if you have a Whirlpool dishwasher made in last 12 years, it definitely has a filter that you should clean monthly. If you cannot find filter after removing lower rack and looking at bottom center, check model manual at whirlpool.com by entering model number on side of door, as some compact models have slightly different location. Even self-cleaning models benefit from spray arm cleaning.