i have old whisper filters, they dont have any bio thing that keeps bacteria. they have the sponge for the carbon to go in and then when its dirty, i throw the cartrigdge out replacing it with a new one. ive heard that whisper filters have came out with a new bio thing that you might have to rinse in water. i am getting rid of most of my whispers and converting to aqua clear filters. i like them better. i have heard that whisper filters are good for smaller tanks though. if i havent replaced my whisper filter in a while, it starts to over flow like you said. if i put a new cartridge in,it doesnt over flow. if it keeps flowing, there may be something cloged in the filter or the motor. maybe you should rinse it again. my method may be the wrong way to do it too. but it hasnt affected my tanks in any way and seem healthy