An increasing number of households across Victoria are installing rainwater tanks either as a source for drinking water, garden and general use or as part of the Governments 5 Star Energy Efficiency requirements for new homes.
Until recent times, many in areas with a 'town water' supply would have found it near impossible to obtain a permit from their local council to install a tank - times change.

For rainwater tanks to meet the 5 Star Energy Rating requirements they must be connected to all cisterns in the home, be larger than 2000 litres and be fed by more than 50 square meters of roof area.
When used in conjunction with a mains water supply, lines must be installed so that the tank operates separately from the water supply system. This prevents water from the tank siphoning back into the mains supply. In serviced areas all tank overflows must be connected back into the stormwater drainage lines. In 'rural' areas water may discharge to the ground provided it is contained within the property boundaries.

There are a variety of tank sizes and shapes available to suit all requirements, but before proceeding check with your local council for any height and placement restrictions.

The size of the tank you require will relate directly to its intended use. Determining how much water is required over a given period, multiplying the roof catchment area by the expected rainfall figures for your area will give an approximation.

The bacterial quality of tank water for drinking purposes will rarely be better than that of mains water unless correct tank installation is carried out, adequate maintenance is kept up and possibly at times the inclusion of chemicals to purify the water.
Water from roof catchments can result in atmospheric pollution, bird and animal faeces, insects, lizards or other small animals being flushed into the tank. Residues from solid wood heaters, which can condense near flues on the roof are another source of pollution.

Fitting an appropriately sized first flush water diverter is one of the most important factors in achieving good quality water.
Determining the correct volume of water to divert is critical. The volume and the type of downpipe system will determine the type, and volume of the diverter. For a 'wet' system, where water is held in the downpipe, the volume held in the pipes should be added to the roof diversion quantity.
Fitting screens to prevent mosquitos breeding is another major requirement.
A good quality inline filter on the house side of the tank is another safeguard.

When purchasing a tank to be used for drinking water check with the manufacturer that the tank material is suitable for the purpose.