Solutions for submetering water in a multifamily

[Justin Dragon]

Good morning all,

I just secured my first triplex in the Hampton Roads, VA and am looking to optimize cash flow. Does anyone have any best practices to equitably charge tenants for water usage? Set up has 1 detached unit with its own water heater, and 2 attached units with two water heaters, one of which supplies water for both attached unit washing machines. I've looked briefly at submetering, but am not deeply knowledgeable, and also wanted to see if there are other creative solutions.

Thanks!

Justin