Autumn Beck said, "Don't be afraid to use bleach"

There are times when a little bleach is necessary. When you buy used it isn't a bad idea to bleach the diapers. There have been extreme cases where a seller passed on a bad virus to an unsuspecting buyer.This ended horrible with the buyer's child becoming very sick.
This is an extremely rare event (I have only heard of it once inmy years of cloth diapering) but for me the thought is enough.

Bleach is also helpful when your diapers have major buildup. I have soft water where we live. Because of this, detergent gets trapped in the diaper fibers causing the diaper to stink, decrease absorbency and create rashes on the baby.When using bleach start the wash and add about ¼ cup to the cycle 5minutes after agitation has started.

I do it this was simply because I don't want to take the chance of bleach sitting directly on the diapers.I suggest doing an extra rinse cycle with very hot water after you use bleach.