Hi Muzza, from another Aussie live steamer.
I have 8000 litres of rainwater tanks, mainly for bush fire fighting supplies in summer and a bit of garden watering. I have started using it for loco water as well, using a Woolworths 'own brand' water filter jug with the replaceable cartridges. The cartridges are good for about 150 litres of water so I should be right for a while. After filtering I store the water in plastic bottles out of the sun and add a little bit of peroxide to kill off any algae.