Yes, rainwater is best. But if you have to, do a pH test on your water - usually alkaline can be mediated to make it neutral (the kind succulents like, for the most part) by adding vinegar.

Years ago I used tap water. I had some plants that slowly declined in health until they died and suspected mineral build-up was working against me. The slow decline reminded me of carnivorous plants dieing because of mineral build-up. I started using collected rain water unless I run out of it. My plants seem to be generally better. However, I didn't have a way to check for mineral problems so I don't know for certain if that was a problem. I've read you can flush out built-up minerals by watering a lot but I'm not sure that works as well as I needed. Also, I prefer to not drench my cacti and succulents.

I will be getting a rain barrel then. The ph is almost 9 and general hardness is in the hundreds, last I checked. I keep tropical fish, so this is something I work with a lot. Rainwater for my succs now, not just my violets. Thanks!

I use rain water as much as possible too. Also water from dehumidifier.