I use distilled water, and add a dash of Sea Salt for electrolytes. Questions have been raised about the fluoride in spring water. Some springs are naturally fluoridated and some are treated by local water companies, so you have to check with the company if you want definite amounts. I've attached a link with a bit of info on amounts of fluoride in some drinking waters. You will need to scroll down to about the middle of the page to see the list.