A bit of water down in the sump, under the filter, is expected: it stops the seals from going dry. A tub floor that's under water is a different story. Check these spots in the same order the water travels on its way out.
1. The filter
Most dishwashers from the last fifteen years have a filter you clean by hand: a cylinder that twists out of the tub floor, often with a flat mesh screen under it. Rinse both under the tap with a soft brush. A greasy, clogged filter is behind this problem more often than anything else.
2. The sump and drain opening
First cut the power: unplug the dishwasher or flip its circuit breaker off. Put on gloves, because some models have a small chopper blade in the sump. With the filter out, feel inside the opening for broken glass, fruit stickers or bits of bone.
3. The garbage disposal
Many dishwashers drain through the disposal, so run it for a few seconds. If the disposal is new, the knockout plug in its dishwasher inlet may still be in place. That's a classic reason a just-installed dishwasher won't drain.
4. The air gap
If there's a small chrome cap beside the faucet, lift it off and clear out whatever is inside. Water spurting from it while the dishwasher drains means the line past it is blocked.
Then run a drain cycle
Use cancel or drain, which on many models means holding Start for about three seconds. Listen closely: a pump that hums but moves no water may be jammed, and if you hear nothing, suspect the pump or the control.
Still holding water after all four checks? That's when a visit makes sense.
