$108
Changes have been made to the Building Code G12 that now mean all hot water cylinders need a cylinder tray or some way of removing water after a cylinder overflow. It does not mention valve failure, but common sense says you would take that into account. Aqualine Cylinder Trays are the obvious way of showing compliance to the building code. It is important that all trays have a 40mm waste outlet.
5.2.3 Safe trays
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. 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 40 mm. 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.