FAQ Search Select a Category BarkBath Cleaning Formulas Cleaning Tips Commercial Products Corporate Deep Cleaners Hard Floor Cleaners Mops, Brooms and Brushes Parts and Accessories Steam Sweepers Vacuums Warranty Web Site and/or go Why is my Upright Deep Cleaner Foaming? Answer: What formula are you using? We recommend only using BISSELL Upright Deep Cleaning formula. Make sure you aren't using any manual formula in the machine because it will foam over.