A properly maintained rainwater tank can provide good quality drinking water. Occasionally there are cases of contaminated rainwater sickness. In urban areas, public water supply remains the most reliable source of drinking water for the community. Water is a valuable resource and rainwater stored in a tank is safe to drink as long as appropriate measures are taken.
You just need to make sure that the parts of your rainwater collection system are made of food-safe materials and that they are properly maintained. Many experts say that untreated rainwater may not be safe for human consumption, even though national guidelines suggest that the risk of getting sick from drinking rainwater is low. As long as rainwater is clear, has little taste or smell, and comes from a well-maintained water intake system, it is likely to be safe and unlikely to cause illness for most users. The answer is yes and no.
In its purest form, rainwater is certainly cleaner than treated water, as it is free of chemicals that can be added as part of your state's water treatment program. But that doesn't necessarily make it safe to drink it, especially from your rainwater tank. Just make sure you select an AS4020 certified water tank, take proper precautions, and make sure your rainwater tank is properly maintained. In these areas, NSW Health supports the use of rainwater tanks for uses not related to drinking water consumption, such as flushing toilets, washing clothes or in water heating systems, and outdoors for uses such as garden irrigation, car washing, filling swimming pools, spas and ornamental ponds, and extinguishing fires.
Proper maintenance of the tank, catchment system, roof, gutters and inlet is essential to ensure a safe water supply and is best done before heavy rain seasons. Tank Shop sells a self-cleaning system for tanks, and many who install it notice much fresher tasting water with no odor, while others are happy to see their toilet water change from a little color to very clear. The microbiological quality of rainwater collected in domestic tanks will be worse than that of many public water supplies. To maintain a safe water supply after the initial dose, 1 gram of calcium hypochlorite or 4 milliliters of sodium hypochlorite per 1000 liters should be added to the rainwater tank and allowed to stand for a minimum of two hours.
If your roof is freshly installed or freshly painted, then it's best to wash it and dispose of the first rainwater runoff if you use the water in your tank for drinking or cooking. Plastic tanks will need some water or should be tied up to prevent them from tipping over in high winds when emptied. Aggressive cleaning methods can accelerate deterioration, for example, by removing the protective layer on the inner walls of a steel tank, which will cause corrosion of the tank. For public water supply), tank size is not such a critical issue and will often depend on taking into account user requirements (garden watering, car washing, etc.) This “first flush” can be used for washing, watering plants, or other non-drinking uses.
Filtering can also remove some, but not all, of the hazardous metals that have been found in many Australian water tanks. Tanks with a “conical slag” base are easy to clean by simply opening the cleaning outlet to allow water to flow with the sludge and then rinsing them with a hose. After cleaning, it is recommended to rinse the internal walls and floor of the tank with clean water. If there is sludge in the tank, it must be removed by siphoning or by completely emptying the tank (dislodged).