If your son or daughter's tush is breaking out, your diapers need a boiling.
Take a large canning pot and half fill with hot water, bring it to a boil, and add about 12 to 18 clean diapers depending on size of pot and 1/2 cup of vinegar. Boil diapers about 1/2 hour stirring regularly. You will see scum come out of the diapers from old detergent and such.
Drain well and wash in washer as usual. Dry cloth diapers outside if possible or on high heat in dryer.