Some years ago I was President ofcan HOA in the Boston area that had a similar problem Our 14 acre complex c9nsisted of a variety of home styles that from about 2000 to 6000 square feet in size, all on a single water meter. When water rates zoomed, many of our owners were concerned with the disparity in usage, but it would have cost a fortune to replumb the complex. Instead we installed a sub-meter at the service entrance to each unit, and then allocated each vill by usage. It worked perfectly!