The Acceptable Solution for Water Supplies G12/AS1, amended 1 January 2017, came in to full effect on 1 June 2017.

Safe trays are required as a means to prevent water damage caused by storage water heaters to household units. 

Paragraph 6.11.3 (a) of Building Code Clause G/12 was amended to remove the following exclusion for when a safe tray under storage water heaters is required - ‘where water could penetrate another household unit within the same building’. This paragraph now requires safe trays under all storage water heaters.

Paragraph 5.2.3 was amended to include the following wording ‘Performance E3.3.2: states that; free water from accidental overflow from sanitary fixtures or sanitary appliances must be disposed of in a way that avoids loss of amenity or damage to household units or other property.' Paragraph 5.2.3 goes on to state ‘An acceptable method of preventing water damage is to locate a safe tray below the water tank (see Figure 4). The safe tray shall incorporate a drain with a minimum diameter of 40mm. Where the tank overflow discharges into the safe tray, the diameter of the safe tray drain shall be greater than the overflow pipe from the tank and comply with Paragraph 5.2.2.’

The previous version of paragraph 5.2.3 required water to be prevented from penetrating another household unit within the same building.

Safe trays are not required in buildings that are not household units, unless the adjoining occupancy is a household unit. Buildings solely used as commercial buildings such as offices or warehouses do not require safe trays. Safe trays are also not required for instantaneous water heaters or boilers.

In short if you are using G12/AS1 as a means of compliance, from 1 June 2017 safe trays are required for all new installations.  

Read more about installing safe trays.