I have a Whirlpool duet Sport with error code F21 - what should I do?

F21 is a code for Long Drain. I would check to see if anything is clogging the pump. If you remove the 3 1/4" hex screws from the bottom panel, you can remove the panel. Behind the panel is a large white pump. You can remove the filter and check to see that nothing is in there that shouldn't be.

If that doesn't help, then you may need a new pump.