Though many cat litter brands claim to be "flushable," it is never a good idea to flush waste matter and litter down the toilet, as clogs can result both from the bulk of the waste matter as well as the litter material. If you find yourself with a toilet clogged by cat litter, you'll need more than a plunger to fix it. Fortunately, there are several strategies you can employ to get rid of the clog and restore your toilet back to working order.
Preparing the Toilet
Because many varieties of cat litter clump when exposed to moisture, the litter has a tendency to clump together and form a near-solid mass in the bowl. To help loosen this mass, pour several tablespoons of liquid dish soap down the toilet and let it sit for several minutes. Then use a plunger to break up the mass into smaller pieces. If the mass is still intact, try pouring boiling water into the toilet followed by a few more tablespoons of dish soap. Then try breaking up the mass again
Clearing the Pipes
If some of the cat litter has gotten into the pipes it will need to be cleared before you can continue cleaning the toilet. To get the cat litter out of the pipe, use a toilet snake to loosen the clumps. Make sure you scrape the sides of the pipes so you don't have residual clumping. Don't be alarmed if you see several bubbles appear in the bowl during this process.
Clearing the bowl
Using a small shovel, pull all the big, wet clumps out of the toilet bowl and put them into a moisture-proof bag. It is OK to leave some residual sand in the bowl, but all large clumps need to be manually removed to prevent further clogging. Once you have removed all the large clumps, throw the bag away.
Plunge and Flush
When all you have left is sand, give the toilet a few final plunges and then flush the toilet. If a clog is still present, try plunging again, using the snake and then flushing again. Even if the toilet is clear, it may take several flushes to get rid of all the sand in the pipes, so make sure to flush a few extra times just to be sure.