Darkoshi

I noticed a dark color in the pik that I put in my mouth. Upon closer examining I realized that the pik AND the handle were caked with mold. I always put mouth wash in the bowl when I use it, dry out the bowl, and dry the rubber gasket where the bowl rests. But you cannot see what is going on in the handle, and this is where the mold rests. There are no instructions for cleaning the Waterpik, except to not use bleach. Bleach is the only thing that will kill mold. I have had good check ups from my dental hygienist since using the Waterpik, but it seems that this is a defect. I don't want to squirt black mold into my mouth. Any suggestions? Does Waterpik know?