A small amount of water in the filter sump can be normal on some models; a pool covering the tub floor usually points to the filter, drain hose, pump, or sink-side connection.
Confirm that the amount is abnormal
Check the manual and note whether water remains after every cycle or appeared suddenly. Clean water in the sump is different from several inches of dirty standing water.
Clean the filter and accessible drain area
Remove food and debris using the intended maintenance procedure. Do not insert objects into the pump or remove internal guards without instructions.
Inspect the drain hose and sink connection
A kinked hose, clogged connection, or incorrect installation can prevent drainage. If it connects through a garbage disposal, make sure that installation was completed correctly.
Persistent humming, leaks, or errors need service
The drain pump, valves, or controls can fail. If accessible checks are clear and water remains, do not continue disassembling the appliance.