Credit: Bluescope Water
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Since water is heavy, most tanks will need a secure base to prevent them from falling over.
If you are going to use a pump, consider a submersible pump to minimise the noise. A pump may not be needed if you can install the tank at a high point or on a stand — although check to see if gravity feed will provide sufficient pressure.
An overflow device is essential because it prevents flooding during a downpour by redirecting excess rain to the stormwater drain.
A backflow prevention device might also be needed."They are often required for below-ground tanks where there is a greater risk of contamination with mains water," says Gary Workman, national training manager for Green Plumbers.
You also need to decide how to maintain a mains water connection.
If your tank has a top-up system it will automatically refill with mains water when it reaches a certain level.
"The advantage is it only costs $250, although you cannot use the tank water on your garden when there are water restrictions," Workman says.
"An interconnection device, on the other hand, guarantees your internal plumbing always has access to mains, but at around $1,000 it is expensive."
Health and safety
While rainwater is generally pretty clean, there are a few precautions you need to take, especially if you want water for inside use.
- Check if your roof is suitable for collecting rainwater
- Avoid asbestos cement roofs and those painted with lead or bitumen-based paints.
- If you are collecting drinking water is also important to remove any lead flashing.
Since rainwater can pick up pollutants from dust, dead animals, and droppings, install a first-flush device on each down pipe to ensure the first few polluted litres are redirected into the stormwater drain.
- Insect screens to keep out mosquitoes are another must, and need to be cleaned out regularly, as do the gutters.
- Every three-or-so years check to see if you need to clean the sludge out of the bottom of the tank.
If you don't want to clean it yourself you can always hire a professional tank cleaner to do the dirty work.
How much will it cost?
It's difficult to generalise costs because it depends on so many variables. A basic 2,000-litre plastic tank, including a first-flush device and plumbing costs will set you back about $2,000 - $2,500, says Workman.
If you include a rebate of, say, $1,150 it will bring the cost down to between $850 - $1,350, he adds.
Installing your tank
"Find a plumber who has done it before," says John O'Byrne. "Otherwise you might find you need to step them through it." Workman agrees, and recommends choosing a Green Plumber who has been trained in how to install rainwater tanks.
Regulations vary widely so don't forget to check with your local council and water authority before you purchase your tank.
Rebates are usually collected once the tank is installed, but check first to see that your installation will meet requirements.