Tenant tube drains slow

[David P.]

I have a first-floor tenant who had their washroom completely gutted out everything new and fixed previously leak and about 7 months ago that leak did minor damage to the basement ceiling washroom. Not once did the 1st-floor tenant tell me that the tube drains slow he decided to take upon himself and fix it he used draino what sure what else he did but water leak to the basement ceiling and walls washroom and made it worse suggestions and how to handle this situation

[Don Gouge]

Quote from @David P.:

I have a first-floor tenant who had their washroom completely gutted out everything new and fixed previously leak and about 7 months ago that leak did minor damage to the basement ceiling washroom. Not once did the 1st-floor tenant tell me that the tube drains slow he decided to take upon himself and fix it he used draino what sure what else he did but water leak to the basement ceiling and walls washroom and made it worse suggestions and how to handle this situation

Exactly what is "the tube"?