Just because the label says "flushable" does not mean it is biodegradable. It simply means that it goes down the drain. Wastewater Treatment Plant staff suggest that people flush only toilet paper and cautions to not flush the following:
Cleaning wipes of any kind (baby wipes, disinfectant wipes, etc.)
Cotton items such as: facial tissues, cotton balls, swabs and pads
Diapers (cloth, disposable, "flushable")
Napkins (paper or cloth) and paper towels
Personal products, or any non-organic material
Toilet bowl scrub pads
These materials don't break down in the sanitary sewer system like toilet paper does. They can block sewer lines, and clog equipment. Backups could occur and may increase the City's maintenance and repair costs.