Damn, I was going to say "the wet kind"......
Hmm, some interesting answers here........I have never liked distilled water.....OCD thing maybe but, distilled is like damaged in my book. Plants react better to other water sources.
Tap water works but, I don't live in a city and my well water is way off.....High bacterial Ir so I run RO......I have run RO for many, many years. I first started when I did SOG ebb trays......It's the shit for hydro as you add a minor amount of Ca/Mg and control the everything you put IN that water.....Nothing in the way to block or slow uptake of nutrients..
In years of growing. I find that if I test the water and the ppm is over 150ppm........I can do far, far better and get more consistent results if I use RO and supplement the Ca/Mg. The well water changes ppms and pH seasonally and with heavy protracted weathers!
Some folks say that they depend on their tap water to deliver the Ca/Mg.....Hmmm, Someone else said that most chems in tap water are not available to growing plants........Those can be true and false at the same time.......IF it's working for you, problem free.......Why change.......If you need to change - RO.....
Lake, pond, river, and stream water can contain a lot more then you expect.....care is advised when using these....
If I could do rain water all year around I would.......Winter gets in the way of that......I do save rain water for making teas during the winter months.....Then to streams, lakes, ponds and rivers for that water..
There's my 2 cents
Doc