Drain Line Clogging and Water - Who is Responsible?

[David Groemping]

A tenant in my basement unit apt clogged the drain line (per plumber report) and water entered their unit in 2 rooms. The water entered via a floor drain that is not visible, hence not up to code. The Lease is very clear they are responsible for clogs they cause, damage from their use, cleaning, and water and moisture in their unit. They are claiming that bc the water entered the unit via a floor drain not up to code, I am responsible for the water entering the unit, damage and cleaning. Before I reply, I wanted to see if their point is valid.

Many thanks, David

[Joseph Gozlan]

Proving they clogged the drain will be challenging unless your plumber has clear evidence (e.g. pulled wet wipes out of the line). 
as for their damage, if you require them to have renters insurance that should be available to cover the damage. 
lastly, code is something that is different from one municipality to another and may things can be not up to code but grandfathered in (e.g. aluminum wiring that was common in the 60s and now is not up to code)