I get asked often if I can install a rainwater tank to act as the supply for the reticulation.
Short answer… No…
What you need to realise is that unless you are planning on having a massive (100 000l tank) there isn’t much point.
Let’s assume you have a 3000L tank. Then assume you have 4 retic stations that run for 15 minutes each at 30L/min
That means you are using 1800L each time you water so you will almost get a week’s worth of watering out of your tank!
But… that assumes it rains.
And in Perth it doesn’t rain much at all when you are allowed to use your sprinklers. So when you need water your tank will be empty. Of course it will fill up in winter, but then you aren’t allowed to turn your sprinklers on!
Get the idea? Its just not a viable proposition in our climate. So rather than spend a substantial amount of money on a tank, pump and fitting you’d be better investing in a quality reticulation system.