Back flushing will work, been there, done that. You need to review with family members what can and can not be flushed down the toilet. Kleenex, baby wipes, paper towels and some toilet papers are a no no. Test your choice of paper...put some in a glass of water, wait and see if it will begin to break down. Septic safe papers usually are a good choice. And always use lots of water when flushing, it will help make the tank drain better.
__________________
Lee & Kathy, and our alarm clock Jake!
2017 Starcraft Autumn Ridge 266RKS 50 amp.
2017 Toyota Tundra Crewmax 4x4, 10-1-2021