The amount of water you can collect is a combination of your root area and the rainfall you receive in your area.
You can use a tank calculator to find how much rainfall you receive in your area. But the amount of water you need depends on how much you consume. We would recommend between 22,500 and 50,000L if you’re a standard family and are not on mains water. However, if you are connected to town mains and would like to use the harvested water for toilets and laundry, we would recommend between 2,000 and 5,000L assuming your a standard family. If you require a water tank just for gardening and car washing, again you would need approx. 2,000 to 3,000L.