Fold the Bumpil in half to a semicircle shape and load it in an empty washing machine. Arrange the pillow so that it wraps evenly around the inside of the machine. Due to the Bumpil's size, wash it alone.
Add the correct amount of detergent to wash a large load of laundry, according to the detergent manufacturer's instructions. Set the machine's temperature to "Cold" (to avoid shrinkage), the load size to "Large," and, if possible, select a "delicate" or "easy" setting and a normal-length wash cycle.
Remove the Bumpil immediately after the wash cycle is complete. Dry it on a large rack or drape it over a clean surface to allow air to circulate.
Pull one clean, standard-size pillowcases over each end of the folded Bumpil. Keep the pillowcases on with every use to minimize the need for cleaning the pillow itself. Wash the pillowcases as often as desired.