Its important to discern between repairing an item and replacing an item, see the Repairs vs Improvements for more information. You are entitled to claim a rental property deduction through depreciating the cost of construction, see the Depreciation – Construction section.
Briefly, if you purchase an item or renovate a building and the cost is greater than $300. The expense must be depreciated. The aim of depreciation is to claim as a rental property deduction, the decline in value of the asset, rather than the total asset cost all in one go.
There are different methods by which to calculate the depreciation to claim each year, but all of which revolve around the concept of claiming the cost of the asset's decline in value. When a new item is purchased, your accountant will prepare a depreciation schedule, outlining the method used and the rental property deduction available each year. If you change accountants, your new accountant will need to access this information.