When the number of soiled nappies reduces (eg. during toilet training), the nappy can be hand washed in hot water with a small amount of laundry detergent, spun in the washing machine and dry pailed, then added to other laundry for main wash.
See Wash Routine Basics, Front Loader Wash Routine, Traditional Top Loader Wash Routine and High-Efficiency Top Loader Routine for more information.