Tenant intentionally wasting water

[Ariel K.]

I have a 12-unit building and after going through a lot of leak checks, my PM and I have come to the conclusion that a tenant or tenants are wasting water - to the tune of 5,000 gallons a day (a normal day is around 800).  There is one meter, so we tried to look at putting a digital submeter, but every plumber says it won't work in our situation.  We know 3 of the units can't be the issue since they either moved in or out while this was happening.  We sent messages to all residents and 3 didn't answer, so it seems like that is the place to start, but does anyone have any ideas on how to figure this out given the limitations?

[Greg Scott]

What has led you to the conclusion that it is malicious?  Have you run to ground all the more common issues?

I'd start by giving all residents the required notice (usually 24 hours) and go inspect the units as quickly as you can.  There is a decent chance you will find a toilet with a busted flapper. 

If that isn't the issue, the next most likely issue is an underground leak.  On older properties, this is very common.  You would need to hire a leak detection company to find out.  The easiest ones to find are hot water leaks because usually the resident complains that their floor is hot.

If you eliminate those, just have your PM stop by the property randomly to listen for running water. You should be able to narrow it down quickly.