The ability to pass on the cost of water charges to tenants has been a bone of contention for landlords for many years. The Residential tenancy Act amended last year now has some clarity around the charges.
It is a question we are frequently asked so here is the extract from the act that we hope should help you.

39 Responsibility for outgoings
• “(1) The landlord is responsible for all outgoings in respect of the premises that—
o “(a) are incurred whether or not the premises are occupied; and
o “(b) are incurred for common facilities.
“(2) Without limiting the generality of subsection (1), the landlord is responsible for the cost of—
o “(a) the general rate (within the meaning of section 13 of the Local Government (Rating) Act 2002) payable in respect of the premises; and
o “(b) insurance premiums payable in respect of the premises; and
o “(c) any body corporate levies payable in respect of the premises.
“(3) The tenant is responsible for all outgoings in respect of the premises that are exclusively attributable to the tenant’s occupation of the premises or to the tenant’s use of the facilities.
“(4) Without limiting the generality of subsection (3), the tenant is responsible for the following charges, incurred during the tenancy, in respect of the premises:
o “(a) electricity and gas:
o “(b) telephone and Internet:
o “(c) supply of water if the water supplier charges for water provided to the premises on the basis of consumption.
“(5) In this section, premises includes facilities that are exclusively for the use of the tenant.”

and if you want to read the act : RTA