A water cistern is the part of a toilet that holds water which is then used to flush the toilet.
I personally think the sewer line also your toilet water goes there.
Look in your toilet.
The water in the toilet tank is used for flushing the toilet, while the water in the bowl is kept at a lower level to prevent odors from escaping.
Toilet tank
The toilet water may not go down due to a clog in the pipes, a malfunctioning flush mechanism, or a problem with the water level in the tank.
A toilet is used to go #1 and #2 and hurl...
The toilet did not add water yet. By the way, If you filled a bucket with water, The water level would go up.
"Water Closet" is a frequently used synonym for "toilet".
After a toilet is flushed, the water and waste go through pipes in the plumbing system to a sewage treatment plant or septic system for processing and disposal.
Goes straight to sewer
The water in the tank is used for flushing the toilet, while the water in the bowl is kept at a lower level to prevent odors from escaping.