Question

what we should not throw the chemicals down the drain​

Answer 1

Answer:

Reasons why you should not dispose of chemicals down drains

Pipes, especially older pipes, can leak at connections or where they have been damaged. ...

Disposing of chemicals down drains can damage your plumbing which can be expensive to repair and also allow those chemicals a direct path into the groundwater.

Answer 2

it can damage drain connection which can lead to leakage

and many other problems too