Partner We have a rockwood 8317rkss and we got the same problem, the waste get stuck at the bend directly under the toilet. Even after using the flush rinse feature, it seems to never completely empty. I have used an adapter that backflushes the tank and that one long process. Few weeks back I got really frustrated and used a chimney sweep brush to clean the pipe under the toilet, I trimmed the flexible rod and made it work on my cordless drill. Messy, but effective. Ours has a protective covering underneath, so gotta wait till warranty has expired before I fix poor design.