What’s the Value of a Rainwater Tank?

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A single inch of rain on a 1000 square foot roof yields 623 gallons of water. That’s a lot! Installing a rainwater tank means you can keep all that water around until you need it, thereby reducing your use of mains water, saving you money, and helping the environment. If you receive enough rain, it might even be possible to make yourself independent from the public water supply.

The environmental benefits of installing a rainwater tank in certain arid regions of the country are so great that the local authorities strongly encourage and may even require them. In Victoria, using a water storage tanks to run your flush toilets is good for an additional star to help you reach the required five stars in your house energy rating for new construction. Even when they’re not required, rainwater tanks make a great source of water for gardening, washing cars, flushing toilets, and other situations where purity is not critical. Why waste precious purified water just to wash your car?

It is even possible to use rainwater tanks as sources of drinking water. Many people feel that if it tastes, smells, and looks fine, it probably is. You should still be very careful, and ideally install a reverse osmosis or similar purification system. There are a number of contaminants and pathogens that aren’t detectable by sight, taste, or smell. Using a rainwater tank as a drinking water source therefore takes more care than just using it for washing. It’s necessary to ensure the correct types of paints are used for the roof, the tank pH is kept under control and a variety of other factors taken into account.

Issues with Using Rainwater Tanks for Drinking Water?

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Rainwater itself is originally pure. As rainwater falls, it picks up environmental pollution in the droplets of water. Once the rainwater strikes the roof, it picks up any airborne pollutants that may have settled on to the roof, as well as any bacteria from birds and small animal droppings en route to the tank. This is particularly a problem in urban areas, where car exhaust and industrial gases may contain hazardous micro-particulates, but it applies to all systems. Even for houses in rural areas, rainwater from tanks must be carefully controlled against contamination.

A study published in Water Down Under 2008 revealed that Melbourne rainwater tanks were contaminated with heavy metals like lead well in excess of drinking water guidelines. Some of the contamination was attributed not to pollution in the air, but to the building materials used to make the roofs. Roofs with lead flashing often had lead levels in the water 50 times higher than the Australian limit. However, there were other contaminants whose source the study authors could not locate. Aluminum, iron, cadmium, and zinc exceeded acceptable health levels too, but the researchers couldn’t see a link between geographic location or materials used in the roof or tank system.

For these reasons and others, when using water tanks as a source of drinking water, health authorities prefer residents use their mains water supply if available. In a properly maintained tank however, there is no reason you should not be able to drink the water. In the Australian Outback people have been doing in for years. Installing filtration is recommended if using rainwater for drinking purposes to ensure harmful bacteria is removed. 

If you are interested in a rainwater tank then I recommend checking out three different suppliers. Manufacturers that I trust include Clark  Tanks, National Poly Industries and Team Poly.