Rainwater Tank

NSW Health suggests that public water supplies remain the most reliable source of good quality drinking water for the community. In urban areas, rainwater tanks should be utilised for non-drinking uses such as flushing toilets, washing clothes and outdoor purposes such as swimming pools, watering gardens and washing cars. This is because public water supplies in NSW are filtered, disinfected, fluoridated and regularly monitored for quality.

The main concerns of the NSW Health Department regarding water supplied via rainwater tanks relate to microbiological and chemical contamination. Maintenance of your tank and the tanks catchment area needs to be conducted to minimise the risk. 

The following things should be avoided in, or removed from, the rainwater catchment area to reduce the risk of water contamination:

• Organic material & treated wood products

• Vehicle exhausts or emissions 

• Exposure of tank water to light

• Lead based paints and lead flashing

• Acrylic paints as they may contain dissolved detergents and chemicals

• Bitumen-based materials

• Mosquitoes / vermin

• Use only high quality pipes and fittings made of drinking water grade materials, not storm water grade materials

• Ensure your tank been flushed with clean water after the manufacturing process

• Have precautions been taken to ensure your tank water will be exposed to minimal light? This may require you to seal the inlets and outlets of the tank

• Your tank should be mosquito and vermin proof, with the inlets and outlets of your tank having secure covers and mesh strainers

• Avoid catching water off your roof near discharge flues from wood fires, kitchen exhausts, air conditioners and hot water systems 

• If pumping is required, ensure the pump size is matched to the primary tank in use. Incorrectly matched pumps can lead to unnecessary energy use.

Council requires a Land Use Application for the installation of rainwater tanks larger than 10,000L. There are no fees associated with this type of Land Use Application. You can access the Approvals Application Form & Guide through Councils website.

An application is required as Council needs to assess how the location of your tank will affect your neighbours, the location of the flow pipe and any potential erosion problems.

The installation of a first flush diverter prevents the first portion of roof run-off from entering the tank. This ensures any dust, leaves, and other contaminants that may have accumulated on your roof are not washed into the tank.

Gutters should have sufficient and continuous fall to downpipes to prevent the pooling of water. Stagnant water encourages algal growth and provides a site for mosquito to breed. A fall of one in 100 should be sufficient.

The following maintenance is required to ensure water quality is maintained in your rainwater tank:

Roof Catchments

Regular inspection of gutters to clear debris, remove over hanging vegetation, and regularly clean all tank screens.

Sludge Removal

Tanks should be examined every 2 to 3 years for the build up of sediment and plant material on the bottom of the tank. This sludge can be removed through siphoning the bottom of the tank or completely emptying the tank. Employing the services of a professional tank cleaner may be the best choice due to confined space issues, tank movement concerns and other safety issues associated with the process.

Disinfecting tank water is not generally necessary unless you expect that the water is contaminated or you have been advised by your doctor. Water filters can be installed at drinking points. For guidelines visit Australian Department of Health site on Rainwater Tanks.

Rainwater tanks can provide an excellent habitat for mosquito’s to breed in. In addition to causing nuisance, certain types of mosquito can be vectors for virus. This is more of an issue in the Sydney and Illawarra Regions with Ross River and Barmah Forest viruses reported to be transported by the mosquitos. The symptoms of these viruses are mainly rheumatic affecting the joints and presenting flu like symptoms.

Mosquito borne disease may become more common in Australia due to rising temperatures and humidity associated with climate change. The Australian Department of Health provides an additional guide to rain water tanks with information on mosquitos in sub-tropical areas of Australia.

By far the preferred approach for managing mosquitoes and other insects is to keep them out of tanks. In addition, rainwater should not be allowed to pool in containers or on surfaces below tank outlets or taps, as this can also provide a breeding site.

Unless in use, all access points excluding the inlet and any overflows should be kept shut and close fitting removable lids or screens fitted.

Tanks water should be inspected for the presence of mosquito larvae (wrigglers).

Further information on preventing mosquitos can be found in the Guidance Manual for the Design and Installation of Urban Roofwater Systems in Australia.

Guidance Manual For The Design and Installation of Urban Roofwater Harvesting Systems In Australia Edition 1(PDF, 1MB)

• Australian Department of Environment & Energy

• Australian Government Sustainable Homes Guide 

• NSW Health Rain Water Tank Guide 

• NSW Plumbing code standards and notes

• Australian Government: Guidance and Use of Rainwater Tanks