Strategies for dividing utility billing

[Matt Zimmerman]

Hey Everyone - 

I have a triplex under contract and am curious on how to approach this situation. The electric is metered by unit but the water is not. Ideally I wouldn't like the tenants to know I'm even paying for the water so they aren't careless. Is there a formula anyone has used to pro rate this cost based off of square footage per unit? Curious on techniques where people have mitigated this issue of being stuck with a large water bill. 

Thanks as always!