Who's Job Is This: Landlord or Tenant?

[Will Fraser]

A tenant recently let me know that they observed an oddly high water bill.  He then let me know that no obvious sources of a leak are known of in the home and no evidence of leaking is happening, but the high water bill is an indicator of a leak somewhere.

This brought up a fundamental question that I wanted to put out to you and learn from you on:  if the tenant pays the water bill (it is in their name with the city) and there is  SUSPICION of a leak, who's responsibility is it confirm (and pay the fees that would be associated with confirming and/or finding the leak)?

I feel like once the leak is found it would clearly be my duty to repair it (unless the tenant caused it somehow), but when it comes to a suspicion of a leak, what would you recommend?

Thanks for letting me stand on the shoulders of giants!  The view is great from up here!