A place I used to work, had lots of customers who put all kinds of stuff down the toilets.
I hate those commercials on TV where the kids are putting stuff in the toilet and flushing it. That is probably what happen where I worked. I can't image grownups putting bars of soap, etc. into the toilet and then flushing.
Sometimes the only option is to use the plunger, a good quality one.
If this is a continuing problem there may be tree roots in the sewer line,
Here is how to make a drain cleaner:
Boil about a half-gallon of water, let it cool a little. You will want the water temperature about like your coffee. Boiling water can crack the porcelain bowl.
Pour 1 cup baking soda and 2 cups vinegar into the toilet. This will create a process that will help to dissolve the clog. This mixture will fizz.
Now you are ready to pour your hot water so that the force of the water can help to clear the clog.
Let this mixture sit in the bowl overnight You might need to do this a second time.
Invasive plants are Earth's way of insisting we notice her medicines.
Everyone learns what works by learning what doesn't work.
I would try Anne's way first and if that don't work I would use lye. The stubborn bacon grease clogs our family tends to get this time of years is because of to many BLT juices end up down the drain. Lye is potassium hydroxide or sodium hydroxide. It is what we use on our farm to make soap and biodiesel. It is extremely aggressive and caution needs to be taken when using. It will only work if the drain slowly goes down. We put it into the sink next to the toilet drain or the toilet. Use only cold water and add about two table spoons full to the sink drain or bowl. Be carful not to get it on any metal or your skin. Run the water for about 15 seconds after adding it and let it settle in the pipes below or flush the toilet. When it gets to the clog it will eat it away. Usually only takes 15 minutes. Hair and greases are no obstacle for it. If its still clogged try it a second time. When the clog is clear run the sink or flush the toilet for a couple minutes to flush the system clean. Please do not use worm or hot water with lye. The high ph becomes exceedingly more aggressive with temperature. If you do happen to get some on your hands wash with cold water for about 10 minutes.
The best place to pray for a good crop is at the end of a hoe!
Is this going to a city sewer ? Or is it going into a septic tank?
If going into a septic tank you may need to look inside it.
I have cleared numerous paper/ log jams at the tank intake.
A little dunking of things at the throat, opened my slow drain up.
Its possible your tank might need pumping.
If your going into a city system, call rotorooter and let them figure it out.
They make a rubber "balloon" that you hook up to your garden hose.
Slide it down the sewer cleanout and when you turn on the water it expands to seal against the inside
then the water pressure comes out the end and shoves stuff down the line
and pushes water through the clog.
It won't remove roots but it will help make a path through them.
Then lye to dissolve maybe hydrocloric acid but not at the same time or they will expand because it's an acid/ alkalye mix.
Or copper sulfate to kill the roots.
Then dig it up and replace the clay tile with plastic pipe.
The Greenhouse of the Future ebook by Francis Gendron