Rainwater tanks can reduce damage to our waterways caused by excess stormwater. They are available prefabricated in above ground or underground models or can be built on site to meet specific site and homeowner requirements. Uncollected rainwater collects toxins and sediment from soil erosion and is deposited in streams, lakes and ponds through our drainage systems. For example, you may end up with dirty water entering your tank if the first-flush diverters don't drain after each downpour due to clogging, or you may lose more water than you collect if the grids or filters become blocked and overflow instead of allowing water to pass into the tank.
The overflow outlet of the tank is connected to a vertical standpipe inside the tank that reaches almost to the bottom of the tank. However, this option requires excavation and, if water is to be used inside the home, the Australian Plumbing Code also requires that a testable backflow prevention device be installed on any water supply in the house and tested annually. For wet systems, first flush units should be installed near the downspouts, and if contamination of the wet system is a concern, another diverter can be used in the tank to remove standing water from the tank pipes. So instead of it getting (and dirt) into the tank, causing the clean water to come out of the overflow, I send the dirty water from the roof directly to the trash if the tank is full.
Any flavor your tank gives to the water will generally diminish after a while, but if you are going to use the water for drinking, pouring the first fill can remove most manufacturing waste. You may need to be able to clean behind the tank to remove leaves and debris, and any first-flush filters or diverters in the tank will need occasional cleaning. If you only intend to use rainwater in your garden, you may not need a pump, especially if your tank is in a tank holder or if your garden is on a slope and considerably below the tank level, gravity is the cheapest pumping system out there. If rainwater and mains water are interconnected (for example, for backup), mains water must be isolated from the stormwater system by an appropriate backflow prevention device or visible air gap, as required by the Australian Plumbing Code.
Just remember that for a given space, a rectangular tank will hold more water than a round or oval tank. When it overflows, this hole is below the water level and therefore the siphon works, but once the water level drops and discovers the hole, air enters the siphon and breaks it, preventing the vacuum from draining the tank. The report also advises verifying that the tank foundations are level and that the tank has a reliable water switch. Using rainwater can reduce water bills, provide an alternative supply during water restrictions, and help maintain a green and healthy garden.
While most rainwater tanks come with a simple outlet near the bottom of the tank, the fact is that this is where the most contaminated anaerobic water in the tank is located. Save even more by sending the water to your toilet, washing machine, or hot water system, but you'll need a licensed plumber to connect the tank to the power grid.
