Cat litter should never be flushed down the toilet.  Litter is designed to absorb and expand.  It may not cause an issue right away in your pipes, but somewhere down the line, it could cause big problems. Some cat litter brands actually advertise that they are flushable.... most things are.  But we still don't flush them.  The prefered method of disposal is to put clumps from the litter box into biodegradable plastic bags and put them in the trash.  Yes, they will end up in the landfill, but not in the district's already compromised and overworked wastewater treatment system.  Thank you so much for your understanding and cooperation,