The only safe water for many carnivorous plants is clean rainwater, deionized water, reverse osmosis water or demineralised water. That is it. Nothing else. Not river water, not tap water, not holy water, not water you import from Switzerland.
Certainly in Adelaide and other parts of South Australia the potable water is not suitable for carnivorous plants. Our advice is to assume your water is not safe for your plants until proven otherwise. An accurately calibrated TDS meter is a reliable way to show the amount of dissolved solids present in the water. We recommend using water with less than 50ppm dissolved solids. Though some other growers report water with as much as 100ppm dissolved solids is fine.
You may come across some bad advice when researching this topic. My favourites are, if you boil the water and allow it to cool down it will be OK for your plants. This is infact a big lie but nonetheless one which tripped me up when I was a kid. Boiling water will not remove dissolved solids, actually it will have the opposite effect. Dissolved solids will become more concentrated as the pure water evaporates away.
Another piece of bad advice is you can safely use spring water. Spring water is loaded with dissolved solids in the form of minerals. Great for us to drink but no good for carnivorous plants. The truth is almost all potable water has a lower TDS than spring water. Again something I learned the hard way when I was much younger. By now you’re probably getting the impression I was a cool teenager.