Re: HOOVER SIX AAA WHISPER
I suspect its the way you have plumbed the appliance into the waste.
all washing machines should be fitted with its own waste pipe and trap assembly and the waste from the washing machine should be a max 6-10 inches into this down pipe to stop any syphoning back into the appliance.
another option is to carry out a boil wash at least once a week to kill bacteria which will grow faster now that the new powders dont carry any bleaches or phosphates which used to keep most of the appliances clean during normal use.
hope this helps
bryan