Normally I’d say be very careful about not paying your full rent, regardless of the reason, but if your water supplier is Sydney Water you can pay the outstanding charges in lieu of rent.
According to the Tenants Union website receipts from Sydney Water count as rent receipts. A factsheet on utilities on the website also provides a form letter you can send to the agent called ‘Unpaid Sydney Water charges’.
Have a look on the TU website page on Utilities to get the full picture.