A Whirlpool washer pump filter is a sieve that catches fragments and small items such as pieces of cloth, change and cards from entering and jamming the drain hose. The filter protects the drain pump from damage that can be brought about by the clogging.
The pump filter can also get cluttered up with debris causing the washer to drain slowly or not to drain at all, in which case it can easily be cleared. The filter is located through the lower access panel under the washer door, on the back of the drain pump. The pump filter is found on certain Whirlpool washer models like the Whirlpool Duet.