flushable cat litter

does anybody know of any cat litter that you can flush and it want hurt the septic system?

Some of the "natural" litters like World's Best (corn) say they're flushable. However, the plumbers I know say that none of them are truly flushable. You have to let the clumps sit in the toilet for 20-30 seconds so they fall apart before you flush. Otherwiset they'll clog up the drain the same way any large clump does.