When any Property in respect of which the Occupier would be liable to be rated to any Sewer Rate made under the Provisions of this or the special Act is unoccupied at the Time of making such Rate, the Commissioners shall rate and assess the Owner of such unoccupied Premises to such Rate, and every such Owner shall pay the Amount of such Rate: Provided always, that nothing herein contained shall affect the Right herein reserved to recover any Arrears of such Rates from any future Occupier of such Premises.