How do I keep bugs from coming through the drain? 
human
I’m not sure I understand what you mean, do you mean keeping bugs away from your sink? 
assistant
From coming up the drain. 
human
Oh, I see!  I’m not sure if I can tell you how to keep bugs from coming up the drain in your bathroom.  I could help you track down some information, if you like.
assistant
How do I keep bugs from coming through the drain? 
human
I’m not sure I understand what you mean, do you mean keeping bugs away from your sink? 
assistant
From coming up the drain. 
human
Oh, I think I see.  Are you saying you want to trap bugs in the drain, so they don’t come up?
assistant