Re: Condo drain in upper unit caused drain in lower unit to leak?
Now that you confessed letting potting soil go down the drain, you are going to have a hard time showing that you were not responsible for the drain clog.
A rectangular block about 4 x 4 x 8 inches is about two liters
The soil may have settled along a horizontal pipe under your sink and gradually redistributed itself over a few months. Then when you put the first auger or snake down, much of the soil went further down and lodged somewhere else.
Or maybe there was other debris in the drain pipe and when your slug of soil came down, that was the straw that broke the camel's back.
If the clog finally occurred just before 4'th floor level then the 4'th floor unit (the one directly below you) will be first to get get flooded from backup from all the units above.
Stop some of your bank autopayments so you can set priorities for manual monthly payments out of your coronavirus stimulus check.