Solution for excessive water bill

I own a unit in a self managed block of 8 2bedroom units.We only have one water meter. Our bill has been paid from the body corporate fund. However, the bills are now exceeding $1000 per quarter which is eroding the committee’s ability to perform other work.

Are we legally able to divide this amount between number per head in each unit? As there is one unit with 7 people living in it (another issue…) 

A plumber has been to inspect our meter and to check for any leakages.