Lift off your washing machine's plastic bleach port. If your washing machine has a matching port for fabric softener, lift this off, too.
Fill both bowls with warm water. Add a 1 tablespoon of dishwasher soap, either liquid or powder, to each bowl. Stir until the water becomes sudsy. Place the bleach and fabric softener port into one of the bowls.
Saturate a scouring pad with the solution and squeeze out the excess. Scrub the inside of your washing machine's basin. Clean away visible detergent and fabric softener buildup from the machine's central column. Rinse the scouring pad and re-saturate as needed.
Wipe the top of the basin, including the underside of the bleach and fabric softener ports, with a scouring pad. Clean the underside of the lid, where buildup tends to form.
Moisten a sponge with cool water and wipe up any leftover soap. Dry the basin, central column and lid with a towel.
Replace the bleach and fabric softener ports before using your washing machine.