A properly maintained rainwater tank can provide quality drinking water and rainwater tanks are widely used as a source of drinking water throughout rural Australia.
Rainwater used for household purposes for drinking, food preparation or bathing should meet water quality guidelines in order to protect you and your family’s health. The water should be free of harmful microorganisms or harmful levels of chemicals. The greatest potential health risk comes from contamination of water with harmful microorganisms such as bacteria and parasites from bird or animal droppings. Rainwater tanks can also be contaminated from roof or plumbing materials.
The microbiological quality of rainwater collected in domestic tanks will be poorer than that of many public water supplies. Occasionally there are cases of illness from contaminated rainwater. However, providing systems are well maintained the risk of harmful organisms being present is low.
In urban areas the town water supply remains the most reliable source of good quality drinking water for the community as the town water supplies are filtered, disinfected and fluoridated, and monitored for quality.
In urban townships, rainwater tanks should be used for non-drinking uses, such as toilet flushing, washing clothes or in water heating systems, and outdoors for uses such as garden watering, car washing, filling swimming pools, spas and ornamental ponds, and fire fighting. Further, use of rainwater conserves the public water supply and helps to reduce stormwater impacts.
Maintaining safe drinking water in rainwater tanks
Preventing the contamination of drinking water
During dry conditions it is important to ensure your tank water remains clean when the rain finally falls.
Dust, leaf litter, bird droppings and the presence of contaminates in smoke, ash and debris from bushfires can contaminate rainwater. It is important to minimise the amount of these from entering rainwater tanks.
First flush diverters prevent the first portion of rainwater run-off from the roof from entering the tank. This reduces the amount of contamination from sources such as dust, leaf litter and bird droppings.
If you do not have a flush diverter installed, you can simply disconnect the tank inlet to prevent the first run-off from entering the tank.
If your tank temperature rises over 30 degrees Celsius (oC), or frequently exceeds 25oC, you should consider applying approved disinfection to your tank water from a qualified contractor to prevent the growth of pathogens such as Naegleria fowleri.
Rainwater tank maintenance
Proper maintenance of the tank, catchment system, roof, gutters and inlet is essential to ensure a safe supply of water and is best carried out before seasons when heavy rain is expected.
Roof catchments and gutters should be inspected and cleared of leaves and other debris every three or four months. Overhanging branches should also be removed where possible. If overhead wires are too close for safety, contact your local power authority for advice.
All screens should be cleaned regularly. Tanks should not be allowed to become breeding sites for mosquitoes.
Tanks should be examined for accumulation of sludge at least every 2-3 years. If sludge is present in the tank it should be removed by siphon or by complete emptying of the tank (desludging).
Where cleaning necessitates entering the tank, take care to ensure adequate ventilation is provided and an additional person is in attendance.
Do it yourself tank cleaning presents a number of risks including working in confined spaces and access into and out of the tank. Do not use fuel pumps or engines near or inside enclosed tanks due to the risk of carbon monoxide poisoning. It is important to be aware of work health and safety guidelines and Codes of Practice (Part 4.3 of the NSW Work Health and Safety Regulation 2011 and Australian Standard AS2865:2009 Confined spaces).
For more information about how to protect your rainwater tank supply, maintain, and clean your rainwater tank, please refer to NSW Health’s page on rainwater tanks.
Disinfection of rainwater tanks
The most common methods to disinfect a rainwater tank is by chlorination, ultraviolet light (UV) irradiation, or through boiling the water. Rainwater can be by disinfected by bringing to a rolling boil, and allowed to cool before drinking. A kettle with an automatic shut off switch can do this.
The Australian Government Department of Health’s Guidance on use of rainwater tanks provides complete information on preventative measures which can be used to stop potential hazards from contaminating rainwater, straightforward monitoring and maintenance activities, and, where necessary, corrective actions.
Filling rainwater tanks with carted water
If you are filling your tank with water from a water carter, ensure that you are being supplied with clean drinking water (potable water). All water carters should comply with the NSW Health Guidelines for Water Carters.