Splitting Water Bill on Tenants

[Eric Maury]

Hi Guys, 

First time turning to BiggerPockets but love the community and could really use some feedback. Right now I own a multifamily--2 units--1 2br, 1 1br with a shared washer/dryer in house. My water bill is being run up every quarter, and I'm paying over $500 each bill. They're using over 130% of the average usage rate and I don't want to continue to float this bill. 

Recently I started to look into sub metering or installing RUBS but both options seem to have issues. The sub-meter seems to be expensive, and I really don't want to take on a few thousand dollar expense to do this. The Radio Utility Billing System seems really affordable and logical but I can't find a company to do this for such a small unit size. Does anyone have any advice, has anyone been in this type of predicament? 

Any and all help is appreciated, running out of options right now.