You will probably need to look into BC tenant laws to see what your rights and responsibilities are for something like this. In my experience (US and condo-based), the owner of the unit is the one that would be held responsible for any damage from a leak originating in their unit--so he or his insurance would have to pay for all repairs (or pay the association insurance deductible if the building is part of a HOA, whichever comes first). Now whether he can come back after you for that expense I would assume depends entirely on a) your lease agreement has anything holding you liable for this kind of damage and b) BC tenant rights/responsibilities, which will dictate whether he could take you to court for something like this.
Something to think about though--even if it turns out he can't legally hold you responsible for the damage, he could still jack your rent/refuse to renew your lease. So if you're up for renewal anytime soon, I'd keep that in mind and have a Plan B for moving out, if necessary.